feat: show and hide mtime and item count columns with 'M' and 'C' respectively

[gosuwachu]

Implements #212

[Byron]

Great work, thanks a lot!

I am really interested in having the refresh key, is this something you are working on or plan to work on? If not, I might even given it a shot (but will happily surrender this to you if you are even remotely interested).

[gosuwachu]

I am not working on it yet, still thinking how to do incremental updates on top of an existing tree. If you want to give it a go feel free.

Is there some chat/discord where it is easy to reach you? I wonder how you are going to do it 🙂

[Byron]

No chat is available and I'd like to keep it that way (there are enough distractions as is). However, I quickly sketched up a PoC which I hope you can pick up and improve on.
It seems surprisingly simple over all, but definitely needs polish.