Add a contributing guide in the readme#25

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SMarechalBE wants to merge 2 commits intoSGG-Modding:masterfrom

SMarechalBE:docs/update-readme

Commits on Jan 30, 2026

docs: refactor readme
SMarechalBE
committed

Commits on Jan 31, 2026

docs: add contributing page with cpp env setup
SMarechalBE
committed