Added a playable preview to the asset pack!

Decided it'd be fun to include a playable preview of the pack in the form of a small game you can walk around in, check it out!

It doesn't have much as of yet (just the dungeon example) but I might expand on it further in the future. Either way, this is a proof of concept to see how I could do this for future asset packs I make.

Also, to everyone who already purchased the pack - the source code is now available as a file you can download!