[FEAT] Update informer

[skyf0l]

As there are often new versions of htb-cli, I'd like to be notified by launching the CLI to install the update. See how it looks with RsaCracker (with the update_informer crate):

$ rsacracker 
A new release of rsacracker is available: v0.6.3 -> v0.6.4
You can update by running: cargo install rsacracker

I think it would be nice to have a one-line update that would also update autocompletion.

[qu35t-code]

> go run . stop
A new update is now available (dev) ! (ece0cda2365f65195470102e20a693fe8b22a3a5)
Update with : git pull

No machine is running

[qu35t-code]

Added