Add visual feedback for document save action

In the content perspective, when editing a content document, clicking the save button doesn't seem to trigger any visible UI action, so editors don't actually know if the save action worked or not.

In case we have performance issues on the site, the CMS responses time out and the CMS backend is too slow with responses to the CMS SPA app. In case the backend already had a critical issue, terminated the session, and redirected to the SSO error page, the frontend CMS application will remain open on the content document editor with no visual changes indicating that the session was corrupted, except that buttons that normally trigger a UI action (like select an image, or the "done" button) will not do anything. In the case of the Save button, the editors don't know if it worked or not because there is no indicator that the action was successful or not.

So would be good if the Save button showed a change, like a button colour change, or shown a notification for few seconds saying if the save action would be successful or not.