Adding note about Manifest v3

[DandelionSprout]

So it seems that the Chromium team has decided to follow through with their war on adblockers, by having a laughably small current rule limit of 35,000 and by (as far as I can determine) removing most of the more advanced syntaxes that recent adblocker versions can use from October-ish onwards. So tonight I've decided to venture a bit around on the GitHub issue trackers of various lists that are included in adblockers, and get them to publicly take a stance against Manifest v3, in order to educate laymen and to establish some kind of pressure on the Chromium team. If they want war, I'll give them just that.

I've turned on the ability for you as a maintainer to edit this pull, should you want to do any changes to the note's text on your own.

[DandelionSprout]

Okay, so it appears that I had most likely misunderstood the Chromium devs' statements on the rollout of v3, as that they'd roll it out to Chrome Canary sometime around August.

Thanks to okiehsch I realised all of a sudden that the release schedule was not set in stone, and that I had most likely misinterpreted "Canary" as meaning Chrome Canary instead of Chromium Canary (having previously forgot that Chromium had beta branches of its own).

So chances are I may have overreacted, but I still think v3 (as it currently looks like during this early testing phase) would be a complete disaster unless they bump user rules to ≥200,000 and ensure support for has and has-text.