fix(framework): Provide a workaround for Firefox 74 shadow root bug (#1347)

Author: vladitasev

packages/base/src/UI5Element.js

@@ -105,6 +105,10 @@ class UI5Element extends HTMLElement {
 				await this._processChildren();
 			}
 
+			if (!this.shadowRoot) { // Workaround for Firefox74 bug
+				await Promise.resolve();
+			}
+
 			await RenderScheduler.renderImmediately(this);
 			this._domRefReadyPromise._deferredResolve();
 			if (typeof this.onEnterDOM === "function") {