Add jupyterhub-sshd-proxy

[batpad]

Thanks to @yuvipanda - this PR just rolls back the conda-forge commit in #23

[batpad]

@sunu hmm not fully sure what's failing on the CI here - let's look at this together tomorrow.

[batpad]

@maxrjones this is very weird, but it seems like some of the code-server extensions are now failing to install?

Would you be able to take a look? Feel free to hit me up for a quick chat - but essentially if you take a look at the last few Actions runs - it does seem like some extensions are sortof randomly sometimes failing to install..

cc @sunu

[maxrjones]

@batpad I'll have time to look at this tomorrow. I think if it's blocking you it would be fine to remove the VS Code extensions for now

[batpad]

I removed a couple of the code-server extensions that seemed to be failing and this builds now. I'll merge this PR, but @maxrjones whenever you have some time, might be nice if you're able to take a look at the extension installs.