extension: Manifest v3 first draft - works minimally on FF, not Chrome

[danielhjacobs]

Will close immediately, since this does not work. Meant to help exemplify what is needed for Manifest V3.

Issues on Firefox: Extension does not activate until Ruffle symbol is clicked (maybe just because it's an unsigned add-on with a modified manifest though); opening an SWF in a new tab does not work (maybe because the persistent keyword no longer works).

Issues on Chrome: Does not work in the current form. Chrome should use declarativeNetRequest instead of webRequestBlocking (does not work on Firefox). Chrome should use "service_worker": "dist/background.js" instead of "scripts": ["dist/background.js"] (does not work on Firefox). With those two changes, I still run into https://stackoverflow.com/questions/70474845/inject-javascript-from-content-script-with-a-chrome-extension-v3 and failure of dist/background.js to register as a service worker (due to errors such as document is not defined), but some sites do work. However, sites that do checks for Adobe Flash Player don't detect Ruffle.

[danielhjacobs]

For declarativeNetRequest, see https://developer.chrome.com/docs/extensions/mv3/mv3-migration/#when-use-blocking-webrequest

Meta bug for declarativeNetRequest for Firefox: https://bugzilla.mozilla.org/show_bug.cgi?id=1687755

For service worker, see https://developer.chrome.com/docs/extensions/mv3/mv3-migration/#man-sw

Issues are as listed on https://blog.mozilla.org/addons/2022/05/18/manifest-v3-in-firefox-recap-next-steps/ and w3c/webextensions#72

It also may be a good idea to allow using Ruffle without the "Open SWF in new tab" functionality by using optional_host_permissions as described in https://developer.chrome.com/docs/extensions/mv3/mv3-migration/#declarativenetrequest-conditional-perms