Fix the default RegExp for link validation to support port and match the beginning.

lib/src/models/rules/insert.dart

@@ -330,7 +330,7 @@ class AutoFormatMultipleLinksRule extends InsertRule {
   // https://example.net/
   // URL generator tool (https://www.randomlists.com/urls) is used.
   static const _linkPattern =
-      r'(https?:\/\/|www\.)[\w-\.]+\.[\w-\.]+(\/([\S]+)?)?';
+      r'^https?:\/\/[\w\-]+(\.[\w\-]+)*(:\d+)?(\/.*)?$';
   static final linkRegExp = RegExp(_linkPattern, caseSensitive: false);
 
   @override