Tweak comment parsing

This is taken verbatim from tree-sitter-c [1], just in case :-).

[1]: https://github.com/tree-sitter/tree-sitter-c

grammar.js

@@ -23,8 +23,8 @@ module.exports = grammar({
     ),
 
     comment: (_) => choice(
-      seq("//", /[^\n]*/),
+      seq("//", /(\\+(.|\r?\n)|[^\\\n])*/),
-      seq("/*", /[^*]*\*+([^/*][^*]*\*+)*/, '/'),
+      seq("/*", /[^*]*\*+([^/*][^*]*\*+)*/, "/"),
     ),
 
     // Definitions {{{

src/grammar.json

@@ -33,7 +33,7 @@
             },
             {
               "type": "PATTERN",
-              "value": "[^\\n]*"
+              "value": "(\\\\+(.|\\r?\\n)|[^\\\\\\n])*"
             }
           ]
         },