Add note about `contributors.json` in CONTRIBUTING.md
Add note about `contributors.json` in CONTRIBUTING.md

revolunet/putaindecode.fr,revolunet/putaindecode.fr,putaindecode/putaindecode.fr,revolunet/putaindecode.fr,putaindecode/putaindecode.io,putaindecode/putaindecode.fr,putaindecode/putaindecode.fr