Update Manifest version from v2 to v3

[PikachuEXE]

Similar issue for another extension: ClearURLs/Addon#326

[danny0838]

We'll do that as late as possible. In short: MV3 sucks.

Migrating to MV3 gains nothing, requires the user to do more configuration for normal functionality, and may introduce issues (since the service worker may be randomly killed and requires a restart when needed, it may cause some network requests not correctly blocked).

We already have the MV3 beta version, whose link is visible in the description of the Chrome Web Store. Test it if you're interested in.

[PikachuEXE]

Agree MV3 sucks
But way too many Chromium browsers in the field (and also Firefox sucks in its own way to get enough people using it lol)
I will test beta version when free thanks ;)