Support raw identifiers

Closes #68

Author: maxbrunsfeld

corpus/expressions.txt

@@ -12,6 +12,26 @@ fn main() {
   (function_item (identifier) (parameters) (block
     (identifier))))
 
+============================================
+Raw identifiers
+============================================
+
+fn main() {
+  (r#abc as r#Def).r#ghi;
+}
+
+---
+
+(source_file
+  (function_item
+    (identifier)
+    (parameters)
+    (block
+      (field_expression
+        (parenthesized_expression
+          (type_cast_expression (identifier) (type_identifier)))
+        (field_identifier)))))
+
 ============================================
 Unary operator expressions
 ============================================

grammar.js

@@ -1416,7 +1416,7 @@ module.exports = grammar({
       $.scoped_identifier
     ),
 
-    identifier: $ => /[a-zA-Zα-ωΑ-Ωµ_][a-zA-Zα-ωΑ-Ωµ\d_]*/,
+    identifier: $ => /(r#)?[a-zA-Zα-ωΑ-Ωµ_][a-zA-Zα-ωΑ-Ωµ\d_]*/,
 
     _reserved_identifier: $ => alias(choice(
       'default',

src/grammar.json

@@ -8176,7 +8176,7 @@
     },
     "identifier": {
       "type": "PATTERN",
-      "value": "[a-zA-Zα-ωΑ-Ωµ_][a-zA-Zα-ωΑ-Ωµ\\d_]*"
+      "value": "(r#)?[a-zA-Zα-ωΑ-Ωµ_][a-zA-Zα-ωΑ-Ωµ\\d_]*"
     },
     "_reserved_identifier": {
       "type": "ALIAS",