Add strict contextual escaping on the $scope for grid controller (#14923)

* Add strict contextual escaping on the $scope for grid controller

* use safe_html filter instead

Author: kasparboelkjeldsen

src/Umbraco.Cms.StaticAssets/wwwroot/App_Plugins/Umbraco.BlockGridEditor.DefaultCustomViews/umbBlockGridDemoRichTextBlock.html

@@ -21,5 +21,5 @@
 
 </style>
 
-<div class="text" ng-click="block.edit()" ng-focus="block.focus" ng-bind-html="block.data.richText" style="margin: 0 20px;">
-</div>
+<div class="text" ng-click="block.edit()" ng-focus="block.focus" ng-bind-html="block.data.richText | safe_html" style="margin: 0 20px;">
+</div>