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/vendor/jquery.are-you-sure.ts

@@ -1,3 +1,4 @@
+// @ts-nocheck
 // Fork of the upstream module. The only changes are:
 // * use export to make it work with ES6 modules.
 // * the addition of `const` to make it strict mode compatible.