Add coords and other features to lichess board
• Add coordinates to chess board in Lichess.org.
• Apply transparency to chess pieces on the board (A slider can be added in a later version to allow the user to adjust transparency, if feature is not implemented by Lichess by then).
• Current background is Lichess's grey background (In future versions, script will detect the user's background and only add coordinates to it, also if feature is not added by Lichess).
• Compatible with board orientation (white/black) and with the Lichess defined hotkey "F".
