feat: build manifest V3

[MikkCZ]

TODO:

• create context menus and their handlers compatible with MV3
• change browserAction to action
• use scripting for content scripts
• split host_permissions from permissions
• disable browser_style in page action and adjust the styling https://developer.mozilla.org/en-US/docs/Mozilla/Add-ons/WebExtensions/user_interface/Browser_styles#manifest_v3_migration
• update web_accessible_resources
• register all listeners synchronously from the background script/service worker https://developer.chrome.com/docs/extensions/develop/migrate/to-service-workers#register-listeners
• register listeners synchronously (listenForRequestsToPontoon, createContextMenu calls, callWithInterval calls, callDelayed calls)
• ensure no duplicate listeners are registered
• migrate to non-persistent background page
• migrate to service worker for MV3 https://developer.chrome.com/docs/extensions/develop/migrate/to-service-workers#update-bg-field, https://developer.chrome.com/docs/extensions/develop/migrate/to-service-workers
• ensure extensions code works for both MV2 (non-persistent) and MV3 and test everything
• bump manifest version
• clean up MV2 code