extesion: update runtime dependencies

extension: update remaining dev deps & tsconfig; add readme

extension: update some more dev dependencies

extension: update some dev dependencies

end2end tests: replace httpbin with postman-echo for delayed load test

extension: fix sidebar display in chrome after previous fix for Firefox iframe load

extension: move sidebar 'load' callback earlier

github actions: add apt update, otherwise it fails to fetch deb repos sometimes

exntesion: switch firefox to use manifest v3

end2end tests: some cleanup

end2end tests: implement more robust checks for extension state

extension: more consistent handling of onMessageCallback

extension: better handling of unreachable pages, at least display icon/notification

end2end tests: fix broken test_new_background_tab

end2end tests: remove hacks from test_sidebar_navigation