Update CONTRIBUTING.md
The https://gitlab.isc.org/isc-projects/bind9/-/blob/main/CONTRIBUTING.md file needs to be updated with our current workflow (the whole thing about how we now generate changelog, etc...)
The https://gitlab.isc.org/isc-projects/bind9/-/blob/main/CONTRIBUTING.md file needs to be updated with our current workflow (the whole thing about how we now generate changelog, etc...)