Update commit lint rules

Not sure if this is something worthy, but its a bit annoying for me tha fact that commit lint has different rules between this repo and, for example, gitlab-terraform-provider

I mean specifically the fact that in this repo, the commit type must be lower-case. However in terraform provider and gitlab monorepo, the commit type must be upper case. Is there any chance we could make this something generic?

@PatrickRice @timofurrer