Fix a number of typescript issues (#32308)

- Prefer
[window.location.assign](https://developer.mozilla.org/en-US/docs/Web/API/Location/assign)
over assigning to
[window.location](https://developer.mozilla.org/en-US/docs/Web/API/Window/location)
which typescript does not like. This works in all browsers including
PaleMoon.
- Fix all typescript issues in `web_src/js/webcomponents`, no behaviour
changes.
- ~~Workaround bug in `@typescript-eslint/no-unnecessary-type-assertion`
rule.~~
- Omit vendored file from type checks.
- `tsc` error count is reduce by 53 with these changes.

web_src/js/utils/dom.ts

@@ -92,7 +92,7 @@ export function onDomReady(cb: () => Promisable<void>) {
 
 // checks whether an element is owned by the current document, and whether it is a document fragment or element node
 // if it is, it means it is a "normal" element managed by us, which can be modified safely.
-export function isDocumentFragmentOrElementNode(el: Element) {
+export function isDocumentFragmentOrElementNode(el: Element | Node) {
   try {
     return el.ownerDocument === document && el.nodeType === Node.ELEMENT_NODE || el.nodeType === Node.DOCUMENT_FRAGMENT_NODE;
   } catch {