Add a CONTRIBUTING.md file?

[ddundo]

Further to our discussions in #102, I just saw https://github.com/github/docs/blob/main/.github/config.yml where they added newIssueWelcomeComment and newPRWelcomeComment. Click on Issues and Pull requests tabs to see how the message looks. I think we could add these and link to the relevant wiki section

We could create this for all repos easily with https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/creating-a-default-community-health-file

Edit: Sorry, this message is added automatically when there is a CONTRIBUTING.md file present (https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/setting-guidelines-for-repository-contributors). Nothing to do with config.yml.