Minor fixes to $crate behavior

Author: Daniel-Aaron-Bloom

src/macros-by-example.md

@@ -134,7 +134,7 @@ Valid fragment specifiers are:
   * `block`: a [BlockExpression]
   * `expr`: an [Expression]
   * `expr_2021`: an [Expression] except [UnderscoreExpression] and [ConstBlockExpression] (see [macro.decl.meta.edition2024])
-  * `ident`: an [IDENTIFIER_OR_KEYWORD] or [RAW_IDENTIFIER]
+  * `ident`: an [IDENTIFIER_OR_KEYWORD], [RAW_IDENTIFIER], or `$crate`
   * `item`: an [Item]
   * `lifetime`: a [LIFETIME_TOKEN]
   * `literal`: matches `-`<sup>?</sup>[LiteralExpression]

src/procedural-macros.md

@@ -350,8 +350,9 @@ r[macro.proc.token.conversion.to-proc_macro]
 When passed to a proc-macro
 - All multi-character operators are broken into single characters.
 - Lifetimes are broken into a `'` character and an identifier.
-- All metavariable substitutions are represented as their underlying token
-  streams.
+- The keyword metavariable `$crate` is passed as a single identifier.
+- All other metavariable substitutions are represented as their underlying
+  token streams.
     - Such token streams may be wrapped into delimited groups ([`Group`]) with
       implicit delimiters ([`Delimiter::None`]) when it's necessary for
       preserving parsing priorities.