Update to Manifest V3

[jprochazk]

Google is killing content blockers by removing webRequestBlocking API from extensions using Manifest v3, and removing support for Manifest v2. This affects Holodex+, because we use that API.

• Investigate if current usage of webRequestBlocking can be replaced by declarativeNetRequest
  • https://developer.chrome.com/docs/extensions/reference/declarativeNetRequest/#type-Redirect
  • https://developer.chrome.com/docs/extensions/reference/declarativeNetRequest/#method-updateDynamicRules
    • videoId, channelId would have to be known before live chat loads
    • dynamic rules have to be cleaned on every browser start, as they persist across browser sessions
• Investigate impact of changing background page to service worker

If either of these turn out to be blockers for using mv3, then we'll have to maintain separate versions for Chrome/Chromium and non-Chromium browsers (e.g. Firefox).

---

Notes

We use webRequestBlocking for:

1. Stripping headers to allow embedding of archive chat
   

   Holodex-Plus/src/background/index.ts

   Lines 33 to 41 in d9b4c60

   	webRequest.onHeadersReceived.addListener(
   	(details) => {
   	return {
   	responseHeaders: details?.responseHeaders?.filter((header) => header.name.toLowerCase() !== "x-frame-options"),
   	};
   	},
   	{ urls: ["*://*.youtube.com/live_chat_replay?*"] },
   	["blocking", "responseHeaders"]
   	);

2. Redirecting a fake embed chat link to embed archive chat - this is dynamic, so may end up being a problem.
   

   Holodex-Plus/src/background/index.ts

   Lines 9 to 31 in d9b4c60

   	webRequest.onHeadersReceived.addListener(
   	(details) => {
   	const q = new URL(details.url);
   	const videoId = q.searchParams.get("v");
   	const channelId = q.searchParams.get("c");
   	const darkTheme = q.searchParams.get("dark_theme");
   	const continuation =
   	videoId &&
   	channelId &&
   	rrc({
   	videoId,
   	channelId,
   	});
   	const redirect = new URL("https://www.youtube.com/live_chat_replay");
   	if(continuation) redirect.searchParams.set("continuation", continuation);
   	if(darkTheme) redirect.searchParams.set("dark_theme", darkTheme);
   	return {
   	redirectUrl: redirect.toString(),
   	};
   	},
   	{ urls: ["https://www.youtube.com/redirect_replay_chat?*"] },
   	["blocking", "responseHeaders"]
   	);

[sphinxrave]

https://stackoverflow.com/questions/74391398/mv3-declarativenetrequest-and-x-frame-options-deny
https://discourse.mozilla.org/t/impossible-to-upgrade-to-manifest-v3-for-extensions-that-require-constant-persistent-listeners/125942/15

[sphinxrave]

For investigating the changes of going from background pages to serviceworker, perhaps it's not a huge deal? Content-Script still works like normal, it's just the background script that becomes more like service worker.

https://stackoverflow.com/questions/71369177/chrome-extension-onmessage-addlistener-vs-chrome-runtime-onmessage-addlistener-o

https://stackoverflow.com/questions/75824421/should-a-mv3-extension-use-chrome-runtime-sendmessage-or-serviceworker-control