Generate allowed users list (for creating issues) using GitHub API

[Kruziikrel13]

I'll look at if we can either auto generate ALLOWED_USERS https://octokit.github.io/rest.js/v22/#repos-list-collaborators or otherwise try this https://octokit.github.io/rest.js/v22/#repos-check-collaborator

However given these are both requests they might not 'just work' in the workflow.