fix(playground): set autorun on clear

Author: OnkarRuikar

components/play-controller/element.js

@@ -102,6 +102,7 @@ export class MDNPlayController extends LitElement {
   }
 
   clear() {
+    this.runOnChange = true;
     this.initialCode = undefined;
     this.srcPrefix = "";
     this.reset();

components/playground/element.js

@@ -80,6 +80,7 @@ export class MDNPlayground extends L10nMixin(LitElement) {
       controller
     ) {
       controller.clear();
+      this._autoRun = true;
       this._storeSession();
       this.requestUpdate();
       const urlWithoutSearch = new URL(location.href);