Fix tutorial diffs (#2642)

While tutorials appear to compile just fine when files are referenced as
strings and omitting the file suffix, it mysteriously breaks the diffing
between each step. This PR fixes things.

Author: stephencelis

Sources/ComposableArchitecture/Documentation.docc/Tutorials/MeetTheComposableArchitecture/02-Navigation/01-YourFirstPresentation/02-01-YourFirstPresentation.tutorial

@@ -25,21 +25,21 @@
         > Note: We conform `State` and `Action` to the `Equatable` protocol in order to test this 
         > feature later.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-01-code-0000")
+        @Code(name: "ContactsFeature.swift", file: 02-01-01-code-0000.swift)
       }
 
       @Step {
         Add a view that holds onto a ``ComposableArchitecture/Store`` of the `ContactsFeature`
         and observes the store in order to show a list of contacts and send actions.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-01-code-0001", reset: true)
+        @Code(name: "ContactsFeature.swift", file: 02-01-01-code-0001.swift, reset: true)
       }
 
       @Step {
         Add a preview with a few stubbed contacts already in the state so that we can see what
         the feature looks like.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-01-code-0002", reset: true) {
+        @Code(name: "ContactsFeature.swift", file: 02-01-01-code-0002.swift, reset: true) {
           @Image(source: "ch02-sub01-sec01-image-0001")
         }
       }
@@ -50,20 +50,20 @@
         button for dismissing, and a "Save" button that when tapped should dismiss the feature
         _and_ add the contact to the list of contacts in the parent.
 
-        @Code(name: "AddContactFeature.swift", file: "02-01-01-code-0003", reset: true)
+        @Code(name: "AddContactFeature.swift", file: 02-01-01-code-0003.swift, reset: true)
       }
 
       @Step {
         Add a view that holds onto a ``ComposableArchitecture/Store`` of the `AddContactFeature`
         and observes the state in order to show a text field for the contact name and send actions. 
 
-        @Code(name: "AddContactFeature.swift", file: "02-01-01-code-0004", reset: true)
+        @Code(name: "AddContactFeature.swift", file: 02-01-01-code-0004.swift, reset: true)
       }
 
       @Step {
         Add a preview so that we can see what the feature looks like. 
 
-        @Code(name: "AddContactFeature.swift", file: "02-01-01-code-0005", reset: true) {
+        @Code(name: "AddContactFeature.swift", file: 02-01-01-code-0005.swift, reset: true) {
           @Image(source: "ch02-sub01-sec01-image-0002")
         }
       }
@@ -87,7 +87,7 @@
         few steps. Go back to the ContactsFeature.swift file where we built the `ContactsFeature`
         reducer for handling the logic and behavior of the list of contacts.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0000")
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0000.swift)
       }
 
       @Step {
@@ -98,7 +98,7 @@
         A `nil` value represents that the "Add Contacts" feature is not presented, and a non-`nil`
         value represents that it is presented.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0001")
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0001.swift)
       }
 
       @Step {
@@ -107,15 +107,15 @@
 
         This allows the parent to observe every action sent from the child feature.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0002")
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0002.swift)
       }
 
       @Step {
         Since a new case has been added to the action enum we must now handle it in the main
         reducer. For now we will do nothing for this case and return `.none`, but soon we will do
         more here.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0003")
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0003.swift)
       }
 
       @Step {
@@ -128,7 +128,7 @@
         automatically handles effect cancellation when the child feature is dismissed, and a lot
         more. See the documentation for more information.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0004")
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0004.swift)
       }
 
       That is all it takes to integrate the two features' domains together. Before moving onto the
@@ -140,7 +140,7 @@
         When the "+" button is tapped in the contacts list feature we can now populate the 
         `addContact` state to represent that the feature should be presented.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0005")
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0005.swift)
       }
 
       @Step {
@@ -152,15 +152,15 @@
         > ``ComposableArchitecture/PresentationAction/presented(_:)`` case in order to listen for 
         > actions inside the "Add Contact" feature.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0006")
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0006.swift)
       }
 
       @Step {
         When the "Save" button is tapped _inside_ the "Add Contacts" feature we want to not only
         dismiss the feature, but we also want to add the new contact to the collection of contacts
         held in `ContactsFeature.State`.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0007")
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0007.swift)
       }
 
       That is all it takes to implement communication between parent and child features. The parent
@@ -182,7 +182,7 @@
         and we have a navigation title and toolbar. We need to figure out how to present a sheet
         in this view whenever the `addContact` state flips to non-`nil`.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0008", reset: true)        
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0008.swift, reset: true)        
       }
 
       The library comes with a variety of tools that mimic SwiftUI's native navigation tools (such
@@ -195,7 +195,7 @@
         store will be derived focused only on the `AddContactFeature` domain, which is what you can
         pass to the `AddContactView`.
 
-        @Code(name: "ContactsFeature.swift", file: "02-01-02-code-0009")        
+        @Code(name: "ContactsFeature.swift", file: 02-01-02-code-0009.swift)        
       }
 
       @Step {
@@ -225,29 +225,29 @@
         `AddContactFeature`. This enum will describe all the actions that the parent can listen for
         and interpret. It allows the child feature to directly tell the parent what it wants done.
 
-        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0000, previousFile: 02-01-04-code-0000-previous)
+        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0000.swift, previousFile: 02-01-04-code-0000-previous.swift)
       }
 
       @Step {
         Handle the new case in the reducer, but we should never actually perform any logic in this
         case. Only the parent should listen for `delegate` actions and respond accordingly.
 
-        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0001)
+        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0001.swift)
       }
 
       @Step {
         Anytime we want the child feature to communicate to the parent we will return an effect that
         immediately and synchronously sends a delegate action. For example, when the "Save" button
         is tapped, we will send the `saveContact` action.
 
-        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0002)
+        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0002.swift)
       }
 
       @Step {
         Go back to ContactsFeature.swift and update the reducer to listen for delegate actions to
         figure out when it is time to dismiss or save the contact.
 
-        @Code(name: "ContactsFeature.swift", file: 02-01-04-code-0003, previousFile: 02-01-04-code-0003-previous)
+        @Code(name: "ContactsFeature.swift", file: 02-01-04-code-0003.swift, previousFile: 02-01-04-code-0003-previous.swift)
       }
 
       The application should work exactly as it did before the "delegate action" refactor, but now
@@ -262,7 +262,7 @@
         ``ComposableArchitecture/DismissEffect``. This is a value that allows child features to
         dismiss themselves without any direct contact with the parent feature.
 
-        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0004, previousFile: 02-01-04-code-0004-previous)
+        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0004.swift, previousFile: 02-01-04-code-0004-previous.swift)
       }
 
       @Step {
@@ -273,23 +273,23 @@
         > Note: The `dismiss` dependency is asynchronous which means it is only appropriate to 
         > invoke from an effect.
 
-        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0005)
+        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0005.swift)
       }
 
       @Step {
         Remove the `cancel` action from the `Delegate` enum because it is no longer needed. We do
         not need to explicitly communicate to the parent that it should dismiss the child. That is
         all handled by the ``ComposableArchitecture/DismissEffect``.
 
-        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0006)
+        @Code(name: "AddContactFeature.swift", file: 02-01-04-code-0006.swift)
       }
 
       @Step {
         Go back to ContactsFeature.swift. We can also remove the `cancel` logic from the 
         `ContactsFeature` reducer and it is no longer necessary to explicitly `nil` out the
         `addContact` state. That is already taken care of.
 
-        @Code(name: "ContactsFeature.swift", file: 02-01-04-code-0007, previousFile: 02-01-04-code-0007-previous)
+        @Code(name: "ContactsFeature.swift", file: 02-01-04-code-0007.swift, previousFile: 02-01-04-code-0007-previous.swift)
       }
     }
   }