Add option to display coordinate on every square

[unicolored]

Hello!

I'm Gilles. This is my first PR, inspired by an old electronic chess game.

This enhancement introduces a feature to display coordinates on every square, which can help with visual learning and quicker square identification.

Key Features:

• New coordinatesOnSquares option in HeadlessState, defaults to false.
• Compatible with both white and black orientations.
• Coordinates adjust based on the ranksPosition to display on the top left or right side of the squares.

Demo:

      Chessground(document.getElementById('board-4'), {
        orientation: 'black',
        coordinatesOnSquares: true,
        ranksPosition: 'left'
      });
      Chessground(document.getElementById('board-5'), {
        orientation: 'white',
        coordinatesOnSquares: true
      });

Testing:

I've tested this feature across various board configurations and verified that the coordinates adjust correctly with changes in size, orientation and ranksPosition.

Looking forward yo your feedback 😊

[ornicar]

Nice, thanks!

[ornicar]

9.1.0 published

[EvanCarroll]

I see the option "Coordinates on every square" in the trainer. But I don't have the setting on lichess.com under Preferences -> Display.
I would expect to find it here https://lichess.org/account/preferences/display

Can we get this added there too. I'd love to use this to learn the coordinates in live games.