Added validation for tags

https://github.com/flarum/core/issues/758

extensions/tags/src/TagValidator.php

@@ -1,4 +1,4 @@
-<?php 
+<?php
 /*
  * This file is part of Flarum.
  *
@@ -18,7 +18,10 @@ class TagValidator extends AbstractValidator
      * {@inheritdoc}
      */
     protected $rules = [
-        'name' => ['required'],
-        'slug' => ['required', 'unique:tags']
+        'name'        => [ 'required' ],
+        'slug'        => [ 'required', 'unique:tags' ],
+        'isHidden'    => [ 'bool' ],
+        'description' => [ 'text|max:700' ],
+        'color'       => [ 'regex:^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$' ],
     ];
 }