Feature request: U2F support

[tidux]

Right now code-server depends solely on password authentication, which is a weakness. If you use code-server over the Internet from a compromised client device, your credentials get stolen. With U2F they'd still be locked out so long as they didn't physically steal a registered key device. My end goal here is to enable code-server to work on shared PCs like at a library or Internet cafe if we ever go back to normal, or just to protect against keyloggers.

[code-asher]

We don't have any plans to implement other authentication modes at the moment. Our recommendation is to put something in front of code-server to handle authentication (this is more secure in the long run anyway).

Related: #1625