fix single-character class attribute

Author: cscheid

crates/tree-sitter-qmd/common/common.js

@@ -122,7 +122,7 @@ module.exports.rules = {
     )),
     commonmark_name: $ => token(prec(1, /[a-zA-Z_][a-zA-Z0-9_\-.]*/)),
     id_specifier: $ => /[#][a-zA-Z0-9_\-.]+/,
-    class_specifier: $ => /[.][a-zA-Z0-9_\-][a-zA-Z0-9_\-.]+/,
+    class_specifier: $ => /[.][a-zA-Z0-9_\-][a-zA-Z0-9_\-.]*/,
 
     commonmark_attribute: $ => prec(3, prec.dynamic(2, seq(
       "{",

crates/tree-sitter-qmd/tree-sitter-markdown/src/grammar.json

@@ -1532,7 +1532,7 @@
     },
     "class_specifier": {
       "type": "PATTERN",
-      "value": "[.][a-zA-Z0-9_\\-][a-zA-Z0-9_\\-.]+"
+      "value": "[.][a-zA-Z0-9_\\-][a-zA-Z0-9_\\-.]*"
     },
     "commonmark_attribute": {
       "type": "PREC",