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/webcomponents/polyfills.ts

@@ -4,10 +4,11 @@ try {
   new Intl.NumberFormat('en', {style: 'unit', unit: 'minute'}).format(1);
 } catch {
   const intlNumberFormat = Intl.NumberFormat;
-  Intl.NumberFormat = function(locales, options) {
+  // @ts-expect-error - polyfill is incomplete
+  Intl.NumberFormat = function(locales: string | string[], options: Intl.NumberFormatOptions) {
     if (options.style === 'unit') {
       return {
-        format(value) {
+        format(value: number | bigint | string) {
           return ` ${value} ${options.unit}`;
         },
       };