fix linting

client/common/lib/elements/livechat.ts

@@ -8,7 +8,7 @@ import { LitElement } from 'lit'
  * Base class for all Custom Elements.
  */
 export class LivechatElement extends LitElement {
-  protected createRenderRoot = () => {
+  protected override createRenderRoot = (): Element | ShadowRoot => {
     return this
   }
 }