fix(SFINT-3248): Replace prepend by insertBefore (#75)

prepend is not supported by antiquated browser among other things (LockerService).
insertBefore works everywhere.

src/components/UserActions/UserActivity.ts

@@ -297,7 +297,7 @@ export class UserActivity extends Component {
 
         const titleSection = this.buildTitleSection(action);
         titleSection.querySelector(`.${ACTIVITY_TITLE_CLASS}`).remove();
-        titleSection.prepend(titleElem);
+        titleSection.insertBefore(titleElem, titleSection.firstChild);
 
         const dataElement = document.createElement('div');
         dataElement.classList.add(DATA_CLASS);