Custom clocks, analysis mode, captured pieces display, copy game code as emojis, and better hotkey explanation!

Hi! I added a custom clocks feature that allows you to control the starting time, the delay (a buffer that resets at the end of your turn), and the bonus (time added to your clock at the end of your turn). In addition, you can now export games and then import them into analysis mode to review them. To export a game press control+S (it's recommended that you do this at the end of a game; especially if it has clocks. If you export a game at the end of a game, you will immediately enter analysis mode on turn one of that game). In analysis mode you can press O to open a different game. There is also a new button on the Online screen that appears when you create a game that allows you to copy the code as 4D chess discord emojis! I also added a display of what pieces have been captures and how many which can toggled with the Q key. Finally, I made the game menu (not the title screen but the one that appears when you press escape from within a game) look less terrible and put a comprehensive list of hotkeys (before I just put the important ones and it looked sloppy and hard to read) and I fixed a bug where the menu would stay open when you exit a game and then go into another game.