[Fix] no-unknown-property: Mark onLoad/onError as supported on iframes

Author: akx

lib/rules/no-unknown-property.js

@@ -68,8 +68,8 @@ const ATTRIBUTE_TAGS_MAP = {
   onEmptied: ['audio', 'video'],
   onEncrypted: ['audio', 'video'],
   onEnded: ['audio', 'video'],
-  onError: ['audio', 'video', 'img', 'link', 'source', 'script'],
-  onLoad: ['script', 'img', 'link'],
+  onError: ['audio', 'video', 'img', 'link', 'source', 'script', 'iframe'],
+  onLoad: ['script', 'img', 'link', 'iframe'],
   onLoadedData: ['audio', 'video'],
   onLoadedMetadata: ['audio', 'video'],
   onLoadStart: ['audio', 'video'],