update v21.8

The "Garden" theme will feature a lot of new vegetation and objects to decorate a magnificent garden, and there couldn't be a lavish garden without a lavish villa...

- Added a 2 tiles-tall bush tileset + more variation of it
- Added a bush arch (4 sizes) and a tile to fill empty bush maze space
- Added a new bush and 2 iron gates

See you and happy game-making! :)