Some work on documentation.

Author: alexrp

doc/installation.md

@@ -1 +1,15 @@
 # Installation
+
+Celerity can be installed as a
+[.NET tool](https://learn.microsoft.com/en-us/dotnet/core/tools/global-tools) in
+two ways:
+
+* To install Celerity globally, run `dotnet tool install celerity -g`. This will
+  allow you to run the `celerity` CLI driver anywhere, assuming you have
+  [set up your `PATH` appropriately](https://learn.microsoft.com/en-us/dotnet/core/tools/global-tools#install-a-global-tool).
+* To install Celerity locally in a .NET-based project with a
+  [tool manifest](https://learn.microsoft.com/en-us/dotnet/core/tools/local-tools-how-to-use#create-a-manifest-file),
+  omit the `-g` option. This will require you to run `dotnet celerity` from the
+  project directory.
+
+<!-- TODO: Add more instructions once we publish signed binaries. -->

doc/language/basic-concepts/agents-and-communication.md

@@ -0,0 +1 @@
+# Agents and Communication

doc/language/basic-concepts/agents-and-message-passing.md

@@ -0,0 +1 @@
+# Modules and Code Reuse

doc/language/basic-concepts/modules-and-code-reuse.md

@@ -1 +1,3 @@
 # Optional Type Checking
+
+<!-- TODO: Fill this out when we have a more concrete plan. -->

doc/language/basic-concepts/modules-and-declarations.md

@@ -0,0 +1 @@
+# Types and Values

doc/language/basic-concepts/optional-type-checking.md

@@ -4,7 +4,7 @@
 expression-statement ::= expression
 ```
 
-Evaluates [`expression`](../expressions.md) (the *result*). If the expression
+Evaluates [`expression`](../expressions.md) (the *value*). If the expression
 statement is the final statement of the enclosing
-[block expression](../expressions/block-expression.md), *result* becomes the
+[block expression](../expressions/block-expression.md), the *value* becomes the
 result of the block expression.

doc/language/basic-concepts/types-and-values.md

@@ -3,3 +3,13 @@
 ```ebnf
 any-type ::= 'any'
 ```
+
+`any` is a special type that, like [`unk`](unknown-type.md), allows any value.
+Unlike `unk`, however, `any` allows you to perform any operation on the value,
+even if the type checker would otherwise be able to prove that a given operation
+is incorrect.
+
+The type of any operation on a value typed as `any` is also `any`. A value of
+type `any` can be assigned to a location of any other type.
+
+`unk` should generally be preferred over `any` wherever possible.