Add GTK inspector page with debug overlay toggles
I've added a few debug overlays to the code as I've worked, but they were all commented out. Now there's a Shumate page in the GTK inspector which allows you to enable debug overlays at runtime. The existing collision boxes overlay is available, and I've added a panel with text information collected from the map layers, and an overlay showing tile boundaries and coordinates.
Edited by James Westman