Chess openings

Here are the areas in which I am confident I can improve over current material:

• Better exploration of the different variations; Graph visualizations can probably help to explore linked openings when we're on an opening page.
• Show side-to-side the board and the squares respectively controlled by White and Black (helpful when learning); To do this we can use the =python-chess= library to get the attacked squares, and render the chessboard with \(\LaTeX\)'s =chessboard= library to keep the same graphic chart.
• Show common threats in openings (which explains why some variations are never played, which is always a bit mysterious as a beginner)