Add ChessMoveHeatmap to #selected-projects of root README

[Phillyclause89]

Hi @niklasf, Love your lib! I'm throwing my silly project idea into the ring for a mention in the next update to this part of your README:

https://github.com/niklasf/python-chess?tab=readme-ov-file#selected-projects

My silly project: https://github.com/Phillyclause89/ChessMoveHeatmap/tree/main

Keep on keeping on!

-Phil