Include dot shield in the default build

[trickypr]

Over the past few weeks, I have been working on getting dot shield to a point where I feel like it is stable enough to include it inside of the main browser. This can already installed via AMO and should be able to update through AMO as well (at least for the moment).

[kierandrewett]

I have been thinking about this too, and I think by the looks of what Mozilla are doing with their other extensions, we should make a GitHub Action that downloads the latest adblocker release and puts it into browser/components/extensions and then we can then load that directory using AddonManager.

[trickypr]

If we go down that route, I should sign the addon for self distribution. If we install the AMO version, it won't update automatically, but if we specify a custom update_url, it will. Updating the addon independently, means we can push out updates independent to browser versions.

[EnderDev-alt]

We could use @trevorthalacker's update server for pushing out adblocker updates

[ItsJamie9494]

Yes, the update server should support that (and if it doesn't I can update it to)