Build mode block highlight update

Untill now, building was a little bit complicated. Especially in the shadowed sides, where you couldn't quite see where the block will be placed. In this update I solved this issue by adding a face highlight to mark where the block will be placed. I hope that this will help you build stuff easier!  

Also removed some small UI bugs.

As always, you can play the game here https://buildncrush.itch.io/game