feat: add rel lang

[robbear]

• Add a test if possible
• Format all commit messages with Conventional Commits

• This PR fixes #

• I have read docs for adding a theme.

• I have read docs for adding a language.
• I have searched around and this is the most up-to-date, actively maintained version of the language grammar.
• I have added a sample file that includes a variety of language syntaxes and succinctly captures the idiosyncrasy of a language. See docs for requirement.

[orta]

Cool, looks good to me thanks

[octref]

LGTM as well. Thanks @orta for merging this.
@robbear Can you provide a link to an official website for rel lang and a link to its spec? I'm thinking that we should add those fields in ILanguageRegistration. I can't find your language by just googling rel lang.

[robbear]

@octref I can point you to https://docs.relational.ai and https://docs.relational.ai/rel/intro/overview/ for now. Should we want to update these links down the road, what would be the procedure? Thank you for the merge!