Bug fix request for janggi variant

[cjssh1002]

1. The image specifications of the janggi board image and the pieces image are different. The image of the pieces is too large.
2. In janggi, there is a "move pass" rule. (turn pass) You need an implementation for this.
3. As I said before, the starting positions of blue and red are different. In janggi, blue should start first move. Replace the plate position or solve the problem. (ex. Flip view)
4. Need rule support for 4 variants of janggi. You should be able to select the "UCI_Variant" option in the Fairy-Stockfish engine settings.
5. PyChess (https://www.pychess.org/) supports PGN of the site, but not winboard's PGN (CECP).
6. We also need the PGN storage function.

[QueensGambit]

Thank you for (re) mentioning the list of bugs and feature requests for Janggi. We will keep them in mind. If s.o. is interested in addressing some of the points, feel free to create a PR.

Some high level source code documentation can be found in our wiki:

• https://github.com/ml-research/liground/wiki