feat: use window_picker for split and vsplit as well

[nagy135]

Adds option to bind split and vsplit versions of "open with window picker".
Not sure if we wanna bind this to some specific key, as I suggested this should be default behavior ...maybe it should be just suggested as an alternative to split/vsplit as a comment after ?
Have to admit that i m in no sense "lua programmer" so please do some testing, but on my setup it works flawlessly

[nagy135]

#314

[cseickel]

This looks good except for:

• You need to target the main branch instead of a release branch.
• You should document the new commands in doc/neot-tree.txt / :h neo-tree-mappings
• You might also want to include a reference to them in deafults.lua and README.md, even if they are just commented out by default.

[nagy135]

it looks like I m little tired at the end of the week ...I also created it from release branch, stripping your netrw fix. Since rebase on main doesnt seem to register here after pull request is already created, I will create a new one fixing these fck-ups