doc: Document TypedUserDefaults usage and update docs

Author: Shibo Lyu

Sources/TypedAppStorage/Documentation.docc/Documentation.md

@@ -1,15 +1,16 @@
 # ``TypedAppStorage``
 
-A type-safe way to save and read complex data structures from `@AppStorage`.
+A type-safe way to save and read complex data structures from `@AppStorage` and `UserDefaults`.
 
-- Use actual `@AppStorage` underneath
-- Support any `Codable` data
+- Use actual `@AppStorage` or `UserDefaults` underneath
+- Support any `Codable & Sendable` data
 - Define the key in the data model
 
 ## Topics
 
 ### Essentials
 
 - <doc:GettingStarted>
-- ``TypedAppStorage``
 - ``TypedAppStorageValue``
+- ``TypedAppStorage``
+- ``TypedUserDefaults``

Sources/TypedAppStorage/Documentation.docc/GettingStarted.md

@@ -69,3 +69,46 @@ In some cases it might make sense to specify a different default value than the
 ```
 
 And you can specify a different store just like `@AppStorage`, if you're using things like App Groups.
+
+### Use outside SwiftUI Views
+
+When you're not in a SwiftUI context, you can use ``TypedUserDefaults`` to access the same type-safe storage:
+
+```swift
+let typedDefaults = TypedUserDefaults.standard
+
+// Reading values
+let currentFruit = typedDefaults.object(of: PreferredFruit.self)
+
+// Writing values
+let newFruit = PreferredFruit(.moderate, .pear)
+typedDefaults.set(newFruit)
+```
+
+Just like `@TypedAppStorage`, the key and default value are automatically inferred from the type's ``TypedAppStorageValue`` conformance.
+
+You can also override the key or default value if needed:
+
+```swift
+// Use a different key
+let specialFruit = typedDefaults.object(
+  of: PreferredFruit.self, 
+  forKey: "specialPreferredFruit"
+)
+
+// Use a different default value
+let fruitWithCustomDefault = typedDefaults.object(
+  of: PreferredFruit.self,
+  defaultValue: .init(.somewhatStale, .banana)
+)
+```
+
+And you can use a different UserDefaults store, just like with the SwiftUI property wrapper:
+
+```swift
+let groupDefaults = TypedUserDefaults(
+  userDefaults: UserDefaults(suiteName: "group.com.example.app")!
+)
+let sharedFruit = groupDefaults.object(of: PreferredFruit.self)
+```
+