"job info" page

[Canop]

The idea would be to display, on a key press, information on the current job:

• its settings
• all the config files involved
• rustc --version, if rustc is found
• rustup show active-toolchain, if rustup is found

[Canop]

I'm not going to start working on this, unless there's a real need or demand.

I'm registering the issue so that people can ask for it.