Update github community health files

[Burgestrand]

These are some administrative changes to the repository and how it's presented on GitHub.

See https://docs.github.com/en/communities/setting-up-your-project-for-healthy-contributions/creating-a-default-community-health-file

To do

• [x] I have read the contributing guidelines.
• [x] ~I have added relevant tests.~
• [x] I have adjusted relevant documentation.
• [x] I have made sure the individual commits are meaningful.
• [x] ~I have added relevant lines to the CHANGELOG.~

[Burgestrand]

Assigning you as a reviewer here @dgmstuart since I explicitly mention you in the security document :)