VSCodium extensions repository support

[i4004]

Is it possible to add repository selection from where to install extensions?
Since VSCodium (https://vscodium.com) uses it's own repository (https://open-vsx.org)

The problem

When using your extension in VSCodium everything works well except it downloads the extensions from https://marketplace.visualstudio.com and not from the https://open-vsx.org

[RafhaanShah]

Also just found out that it can't quite sync extensions between Code-Server and a normal VS Code install and ends up removing most extensions whenever you sync from one to another 😬

Maybe a setting to disable auto removal and / or installation of extensions when syncing also would help? (or something like storing the extension repository when backing up / per-host extensions though that sounds a lot more complex, but I think the vs code extensions API provides the downloadUrl)

[nonoroazoro]

I'm not sure if we can download extensions from https://open-vsx.org/, but I'll check it out.

@RafhaanShah That was unexpected, should not remove extensions while syncing between different VSCode versions.