[Feature] Show tower range while placing it

[Yorok0]

A QoL suggetion about terrain grid. (with a picture)

[concept] This is not new idea. Showing color squares to indicate where you can build and the range of your diffensive buildings like towers/castles only when you are build a building. This is very common in the modern RTS games. The advantage is we don’t need terrain grid to measure the range of buildings anymore. Besides, indicating the unbuildable terrain can avoid the invisible gaps when we build walls.