Takground: give the option to cancel a move

[UlisesTorrella]

Problem: If you start to move many squares in one move you can't go back, and if you hit a wall or the end of the board you are stuck and must f5 the site to keep playing.

Partial solution: Use esc key to cancel a move and go back to the begining of the move.

This changes apply only at ui/takground, in ui/takground/src/board.ts the function takMove splits the behavior of a simple move (that hits the backend) and a building move that is reflected on the client board but not server side. Also this component's state (ui/takground/src/state.ts) has a buildingMove attribute, to keep track of the UCI move to be sent. The idea would be to apply this backwards to get the board in the previous state (see the state pieces attribute). When the state of the board changes you can render it, see render function at src/render.ts.

To have in mind, in the future it would be useful to go back while building a move to an intermediate state (e.g only 1 square behind, not the entire buildingMove)