Allow string prefixes to be either case (#19)

* Allow string prefixes to be either case

* Add test cases

* Regenerate parser

Author: p-e-w

corpus/literals.txt

@@ -92,7 +92,9 @@ Strings
 '"ok"'
 r'hi'
 ur"bye"
+UR'bye'
 b'sup'
+B"sup"
 `1`
 "\\"
 "/"
@@ -110,6 +112,8 @@ string"
   (expression_statement (string))
   (expression_statement (string))
   (expression_statement (string))
+  (expression_statement (string))
+  (expression_statement (string))
   (expression_statement (string)))
 
 =====================================

grammar.js

@@ -705,7 +705,7 @@ module.exports = grammar({
     ),
 
     string: $ => token(seq(
-      repeat(choice('u', 'r', 'b')),
+      repeat(choice(/[uU]/, /[rR]/, /[bB]/)),
       choice(
         seq('`', repeat(choice(/[^\\`\n]/, /\\./, /\\\n/)), '`'),
         seq('"', repeat(choice(/[^\\"\n]/, /\\./, /\\\n/)), '"'),

src/grammar.json

@@ -3393,16 +3393,16 @@
               "type": "CHOICE",
               "members": [
                 {
-                  "type": "STRING",
-                  "value": "u"
+                  "type": "PATTERN",
+                  "value": "[uU]"
                 },
                 {
-                  "type": "STRING",
-                  "value": "r"
+                  "type": "PATTERN",
+                  "value": "[rR]"
                 },
                 {
-                  "type": "STRING",
-                  "value": "b"
+                  "type": "PATTERN",
+                  "value": "[bB]"
                 }
               ]
             }