fix: tweak escape sequence and identifier rules

Author: amaanq

grammar.js

@@ -193,7 +193,7 @@ module.exports = grammar({
     ),
 
     _escape_sequence: $ => choice(
-      prec(2, token.immediate(seq('\\', /[^abfnrtvxu'\"\\\?]/))),
+      prec(2, token.immediate(seq('\\', /[^bfnrts'\"\\]/))),
       prec(1, $.escape_sequence)
     ),
     escape_sequence: _ => token.immediate(seq(
@@ -1266,7 +1266,7 @@ module.exports = grammar({
     super: $ => 'super',
 
     // https://docs.oracle.com/javase/specs/jls/se8/html/jls-3.html#jls-IdentifierChars
-    identifier: $ => /[\p{L}_$][\p{L}\p{Nd}\u00A2_$]*/,
+    identifier: _ => /[\p{XID_Start}_$][\p{XID_Continue}\u00A2_$]*/,
 
     // http://stackoverflow.com/questions/13014947/regex-to-match-a-c-style-multiline-comment/36328890#36328890
     comment: $ => choice(