[Feature Request]: arglist mode

### What?

It would be great if bufferline could show the argument list (arglist) instead of the buffer list.

There could be a new mode "arglist", which then would:

1) Show the arglist as tabs.
2) Closing a tab would remove the buffer from the arglist.

### Why?

I like to use the argument list to keep track of the primary files that I want to edit and move between them. The argument list is always a subset of the buffer list, and I find it better suited for that because it doesn't grow over time just because I quickly open some file to check out something.