UI: The 9-Slice (Patreon)

I decided to break up the UI theme into several parts and this is the first one. The 9-slice (and the 3-slice) is, in my opinion, the basic element of every UI and a good place to start, since you can reuse it pretty much everywhere.

Here's a quick reference of what I like to call the parts of the 9-slice and the 3-slice