Update [broken down stone walls]

Heya!

I have added a 4-directional version of the stone walls from the main tileset, as well as some broken down walls. So now you can use the tiles to make some ancient, overgrown ruins.

I am thinking of adding some aztec village tiles in the near future, as I have had some time to research ancient aztec architecture and the ways their daily lives were structured and would love to have my tileset reflect that. As one result of this research, I have already worked on some ground tiles that can be used to make chinampas, or swimming gardens, which the aztecs built in the lake surrounding their main city in order to gain more fertile land for agriculture. So there will be more additions in the future!