chore: add initial CONTRIBUTING.md
chore: add initial CONTRIBUTING.md

kgislsompo/valdr,NFC-DITO/valdr,kgislsompo/valdr,PesanskiGoran/valdr,PesanskiGoran/valdr,NFC-DITO/valdr,netceteragroup/valdr,SoftwareCraftsmen/valdr,SoftwareCraftsmen/valdr