chore: setup initial repo

[Parkreiner]

This commit lays the groundwork for moving all our Backstage plugin logic into a separate repo that will (eventually) become public and fully open-sourced.

Notes

• The vast majority of the code comes straight from the official scaffolder, or was copied directly from the previous repo. If I didn't leave a comment on the file, it should be safe to ignore it.
• In theory, the Coder Backstage plugin can be launched in isolated dev mode. As in, you will get a dev page with the plugin rendered inside it. However, I couldn't figure out how to get the Proxy available in dev mode (since it technically is a backend plugin), and there aren't any docs for this specific use case. So our code is right, but every query that gets sent out will just hang until the 20-second timeout. I have a thread opened in the Backstage Discord, and am hoping to hear back soon

Changes to watch out for

• There was a bug with the auth code that wasn't obvious until the proxy broke
  • I accidentally had the boolean for checking whether the component was mounting flipped the wrong way
  • Only reason it wasn't obvious is that we were getting back a response from the Coder API too quickly

[Parkreiner]

@code-asher Yeah, I've been wondering about the API factory stuff, too. It just feels weird that the main documentation for proxying makes no mention of them, and they just say to use the native fetch

There is this example page, though, which makes use of the discoveryApi. Hopefully this would do the trick, but I've got two big questions (just thinking out loud):

1. I'm guessing that the plugin would inherit all the config options from the root directory, but we would need to make sure that holds up, and that the proxy properties are being passed down
2. The DiscoveryApi looks pretty straightforward (it only has one function), but I don't know if there are any limits on when it can be called. Like, does it break if it's not set up with the right providers, and would those be available in isolated mode?

Still, once I get the auth PR done, I'll fiddle around with things, and see if I can't get them working

[code-asher]

Awesome, yeah I think we can punt on the API thing since running from the root works perfectly fine, but curious to see what you turn up!