Add docs to explain whether `move` supports directories as destination

[Pomax]

Given that mv somefile.txt textfiles will happily move a file somefile.txt into a dir textfiles, one might expect move('somefile.txt', 'textfiles') to work, but the docs currently do not explain what a valid dest is. Could the docs be amended to make it explicit whether dest must be a file path, or whether any path is valid?

[RyanZim]

Sure, PR welcome.

[Pomax]

Just a friendly reminder that "PRs welcome" isn't really the best phrase to use. To people who file issues, it's effectively a polite way to say "if you want this, go do it yourself", and is one of those phrases that seemed like a good idea when it first popped up, but actually hurts a project more than it helps. A "Good idea!" response and then setting some labels like "docs", "enhancement", and "help wanted" to signal this probably won't get done by the core team itself unless someone has a spare moment is by far the more welcoming approach.

(I will unfortunately not be filing that PR: I'm weeks deep into a 100+ page open source project documentation rewrite already, and have enough on my plate that filing docs improvement requests is the best I can do right now)