added leela chess zero engine (cpu version) and stockfish 16

[KudahShambare]

Purpose

Added 2 additional engines

Pre-merge TODOs and Checks

• (exclude checks that are not relevant for your feature)
• PGN file loads correctly
• Navigating through the move history works
• Starting the engine shows moves (test for both sides)
• Selecting a different variant loads a new board with the variant and you can make moves on the board
• In Crazyhouse the pocket pieces are shown and you can drop pieces

[QueensGambit]

Hello @KudahShambare ,
to my knowledge, Lc0 and native Stockfish 16 only support chess and chess960.
Moreover, the code for downloading the binaries is missing and the logo of Lc0 is upside down.

[KudahShambare]

@QueensGambit Thanks for the feedback let me fix the issues

[KudahShambare]

@QueensGambit just a quick question. If I download the binaries and insert them into the engines directory. Do I need to also include the code to download it from it's main repository?

[QueensGambit]

Hi, I would prefer that you don't upload binaries but update the postinstall.js script accordingly.
https://github.com/ml-research/liground/blob/master/scripts/postinstall.js#L89-L104