Investigate switching to protocol URLs for installer commands

[asportnoy]

The RPC method of install commands is not the best and has various issues, for example content blockers. We should investigate whether we can set up a protocol URL instead, which I think is more similar to what a lot of apps do. Some things to explore:

• See if we can set up our own replugged:// protocol within Discord's electron without removing their own discord:// protocol
• Set up an external application handling the replugged:// protocol and relaying that to Discord. Important here is that it will need to work properly on all OSes and be lightweight, following our principles.
• Add our own routes to the built-in discord:// protocol. This is probably the easiest option. One drawback though is it seems like all Discord platforms use the same protocol with Canary taking priority for me (might just be due to install date). If users have a version of Discord that's not plugged and that's the one that receives the request, it won't do anything and we probably won't be able to detect that.

Ideally, we'd also be able to send data back to the browser with these links but I don't know if we can use fetch with protocol links.