===== Anzeigen eines Spinners / Ladeanzeige ======
\\
https://www.jqueryscript.net/loading/Minimal-AJAX-Loading-Spinner-Plugin-with-jQuery-pleaseWait.html\\
https://asdw.de/bitte-warten-symbol-ueber-ein-fenster-einblenden/\\
https://makitweb.com/display-loading-image-when-ajax-call-is-in-progress/\\