Made a simple standard terrain format tileset for doing terrains with procedural generation.

Did notice some glitches in the terrains when drawing with walls using the brush tool and then drawing with floors so the tileset image needs some sort of editing, but works perfect for terrains when just laying down a big rectangle of walls and then running the floor brush terrain through that, which I believe is what we're doing with the Walker procedural generation algorithm.

Anyway, can update the tileset later to perfect it, just want to get the Walker procedural generation unblocked.

Made a resources folder. Saved the terrain tileset resource as resources/terrain_procgen_tileset.tres, and the tileset image itself as assets/tilemaps/procgen_terrain_tileset.png.

Also saved a couple other tests of terrains and tilesets that contain more of the tiles from the original tileset but I couldn't get them working great with terrains.