add `cmdline_output_to_split` preset to docs/readme

[jrnxf]

cmdline_output_to_split is only passively referenced in the Views section...

cmdline_output	split	split used by config.presets.cmdline_output_to_split

...but not called out as an available option in the Configuration section.

Though, if you're willing to consider, I think changing the suffix of this preset (and the long_message_to_split) from _to_split to _to_cmdline_output makes more sense, since that's what it actually does. Since a user has the ability to change the view for cmdline_output, this naming choice can easily fall apart, likely causing more confusion than it's worth.

It also begs the question of whether or not this preset should even exist, IMO. Shouldn't all cmdline_output go to where the user has cmdline_output specified? That being said, I understand it's just a nice-to-have preset, so keeping it around isn't really a bad thing, even though I'd still recommend changing the suffix if it does stick around.

Cheers! Dank je for great plugin. I've picked up on a few other bugs that I'll make tickets/PRs for when I have the time!

[folke]

Hi! I'm basically waiting for https://github.com/neovim/neovim/issues/21044 to be fixed before "graduating" this feature.

Without that issue fixed, it's not ideal...