doc: add compact directories recipe

[chkhetiani]

Problem: I work mainly in Java and have many directories that are nested with only one sub-directory.

Solution: I created this snippet that, when pressing "oo", recursively opens a directory if it has only one sub-directory. I thought it might be useful for others.

Problem: Unfortunately, oi.open(dir) doesn't support a callback after the view has been updated, so I had to add vim.wait(50).

If anyone can suggest a better solution, I'm open-minded, as obviously wait is a hacky solution.