feat(rulesets): add script

[sgoudham]

This PR adds a deno script (main.ts) that will be responsible for modifying rulesets at scale across the organisation.

TODO:

• Implement all CRUD actions (currently only reads/lists the rulesets)
• Implement some sort of dry-run behaviour (effectively AWS CF Changesets)
  where we can see what it's going to do before it does it (can be cut from the
  scope of the PR if it proves too difficult/tedious to implement)
• A nicer CLI interface
• Add an exception list of repositories that we don't want to apply certain rules to.
• Update documentation

It's worth noting that at some point in the future, I'd hope to see scripts
like this get converted into Golang as part of catppuccin/cli as the CLI
should be as useful to the leadership team as it should be for "normal" users.
I can dream...

[uncenter]

This should probably be read via https://docs.deno.com/runtime/manual/basics/env_variables/ instead of as an arg. This is how it is done in userstyles Octokit stuff as well FYI.