feat(filesystem): open in right below or left above split

[Blackmorse]

This pull request addresses a common scenario where I often open files in a split, but I want control over whether the split appears on the left or right relative to the last buffer. With this update, I've introduced the option to open files using rightabove or leftbelow vs. This enhancement provides more control over split placement, offering flexibility based on user preference. I believe this feature could be beneficial for users who seek a more tailored split behavior.

[cseickel]

Since we have a vsplit, it make sense to have these other variations as well. For completeness, you should also have version of the new command available in the git_status and buffers sources.

There should also be documentation of the new commands in :h neo-tree-navigation.

[Blackmorse]

@cseickel , thanks for you review

I've added documentation for the new command.

Regarding to support for git_status and buffers sources, I believe that new commands are already available for them, since they should be added by the call of _add_common_commands at <source>/commands.lua (the same as for split and vsplit)

[cseickel]

Regarding to support for git_status and buffers sources, I believe that new commands are already available for them, since they should be added by the call of _add_common_commands at <source>/commands.lua (the same as for split and vsplit)

You're absolutely correct, sorry about that.