Switch to manifest version 3 (mv3)

[SebastianZimmeck]

As Firefox is switching to manifest version 3 (mv3) in a couple of months, we should keep an eye on if functionality is breaking, what we need to change, etc. I tend to think that the impact will be a bit more limited than Chrome's switch to mv3 as it is my understanding that Firefox intends to keep some of the deprecated APIs around. However, at the beginning of next year, when Chrome is making the switch, we should address this.

Currently, the timeline of Firefox's switch to mv3 and which APIs will be deprecated is unclear but will become more clear over the next couple of months. Here are some official resources:

• Manifest v3 in Firefox: Recap & Next Steps
• Manifest V3 Firefox Developer Preview — how to get involved

Please everyone keep this on the radar. We do not want to wake up one day and everything is broken (and we can't even update anymore on the Firefox Store).

(cc'ing @harkous)

[SebastianZimmeck]

• Manifest v3 signing available November 21 on Firefox Nightly

[danielgoldelman]

• https://extensionworkshop.com/documentation/publish/distribute-manifest-versions/
• https://extensionworkshop.com/documentation/develop/manifest-v3-migration-guide/

[SebastianZimmeck]

@jjeancharles, can you look into whether we need to make any mv3 changes? Is it already discernible when and what changes, if any?

Here is the parallel OptMeowt issue.