support statusline option in win_config

[ceuk]

To allow customisation of the stausline in the file panel win

e.g.

{
  type = "split",
  statusline = " "
}

..would essentially disable the statusline for the file panel

--

I can have a crack at implementing this if I get a sec

[sindrets]

Sure, I would appreciate if you submitted a PR for this :)

We might as well go all the way though: allow win_config to have a winopts field, that is a table of window option names mapped to values. This way uses can set any window options. Not just statusline.

Example:

{
  type = "split",
  winopts = {
    statusline = "foo bar",
    cursorcolumn = true,
    winhl = "Normal:MyNormal",
  },
}

win_config is implemented in this file.

[sindrets]

@ceuk Are you still interested in implementing this?

[ceuk]

Hey, yeah, got a few hours of downtime so going to see if I can get it done now

[ceuk]

@sindrets is it worth giving bufopts the same treatment do you reckon?

[ceuk]

PR is ready to have a look at :)