Update all-contributors

[honno]

In the README we have an all-contributors listing that was last updated 2 years ago. It'd be nice to get that updated.

We can first and foremost do a run with their CLI to capture the GitHub-repo contributions, which seems fairly trivial. We might want to consider an automated process for this, or maybe we can formalise a process to update all-contributors before every spec release. Automated processes and spec releases is something I've had in mind a lot for #505.

We can also add contributors manually, which is especially useful for those who've contributed to the spec and its adoption outside of this GitHub repo... although it seems we'd really need someone to champion that effort, which I doubt any of us our interested in. Notably there's a workflow we could try adopting where we ping their bot to add contributors. I think it's fine if we accept this isn't going to happen much, just gladly accept bot pings or PRs that add contributors when it comes our way.