Update Docker file name patterns

[oatovar]

The Dockerfile.* pattern is a common naming scheme when there's more than one file in a repository. Similarly, this can also be extended to Containerfile.* files. You can see this in this build-images project, and most projects under the security-products group.

[oatovar]

@tancnle Could you do this review? 😄

[tancnle]

Thanks @oatovar. The PR LGTM 👍🏼

❯ ./bin/rougify guess Dockerfile.foo
{ tag: "docker", title: "Docker", desc: "Dockerfile syntax" }

On a side note, it seems that GitLab already detects the correct syntax (example) 🤔

[oatovar]

@tancnle I achieved that one with a custom .gitattributes 😅 Thank you for merging this!