Tiled Support update

Hello!

I realized Sewers didn't got the Tiled improvement update so here it is ^^

I also did a new sample map in Tiled.

Quick note: In the next weeks I'll start to work on the next asset.

edit: I also added premade corners in case you don't want to use Tiled and have no access to autotile in the game engine you're using.

Thank you very much for your support!