Add types to various low-level functions (#31781)

Adds types to various low-level modules. All changes are type-only, no
runtime changes. `tsc` now reports 38 less errors.

One problem was that `@types/sortablejs` does not accept promise return
in its functions which triggered the linter, so I disabled the rules on
those line.

web_src/js/features/stopwatch.ts

@@ -27,7 +27,7 @@ export function initStopwatch() {
     stopwatchEl.removeAttribute('href'); // intended for noscript mode only
 
     createTippy(stopwatchEl, {
-      content: stopwatchPopup.cloneNode(true),
+      content: stopwatchPopup.cloneNode(true) as Element,
       placement: 'bottom-end',
       trigger: 'click',
       maxWidth: 'none',