feat: build manifest V3

[MikkCZ]

TODO:

• [x] create context menus and their handlers compatible with MV3
• [x] change browserAction to action
• [x] use scripting for content scripts
• [x] split host_permissions from permissions
• [x] 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
• [x] 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
• [x] 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