Draft: docs/compile: Create initial compile docs

I wasn't sure of the status of this project, but I had some extra time on my hands and wanted to somehow provide an updated Win32 compile guide. Since the Wiki isn't editable, I thought this might be meant to replace it.

The documentation for cross-compiling for Windows has been written and is included, but all other pages are stubs and direct users to the appropriate existing guide on the VideoLAN wiki.

Please let me know if I'm in the wrong place, or if I ought to make some changes to what I have here.