feat: support half-open intervals

Author: ribru17

grammar.js

@@ -156,7 +156,13 @@ module.exports = grammar({
     optional: quantifierRule(_ => '?'),
     count_quantifier: quantifierRule($ => seq(
       '{',
-      seq($.decimal_digits, optional(seq(',', $.decimal_digits))),
+      choice(
+        seq(
+          $.decimal_digits,
+          optional(seq(',', optional($.decimal_digits))),
+        ),
+        seq(',', $.decimal_digits),
+      ),
       '}',
     )),