Use github app token for pushing changes

[stefpiatek]

Setup using SAFEHR PR app to generate an access token so that the action will run when it commits to the branch. That way we can have the markdown check as required for pull requests

Changes required for this to be workable

• Use github application for checking out, and pushing
• Ensure that we don't get stuck in a loop of commits from the bot if we have randomly generated md files
• Use mermaid instead of R package for writing out graph - output html changed each time
• Make drugs order reproducible
• documented setup of gihub app in slab: https://uclh.slab.com/posts/setting-up-a-github-app-to-commit-to-a-repository-2sjfd3ae

[milanmlft]

Very kewl 🤖