Add CONTRIBUTING.md

CONTRIBUTING.md

@@ -0,0 +1,33 @@
+## How to contribute
+
+### Reporting bugs
+
+If you find a bug in DOLFINx, please report it on the [GitHub issue
+tracker](https://github.com/fenics/dolfinx/issues/new?labels=bug).
+
+
+### Suggesting enhancements
+
+If you want to suggest a new feature or an improvement of a current
+feature, you can submit this on the [issue
+tracker](https://github.com/fenics/dolfinx/issues).
+
+
+### Submitting a pull request
+
+To contribute code DOLFINx, create a pull request. If you want to
+contribute, but are unsure where to start, have a look at the [issues
+labelled "good first
+issue"](https://github.com/FEniCS/dolfinx/issues?q=is%3Aopen+is%3Aissue+label%3A%22good+first+issue%22).
+For substantial changes/contributions, please start with an Issue or
+start a discussion on Slack.
+
+On opening a pull request, unit tests will run on GitHub CI. You can
+click on these in the pull request to see where (if anywhere) the tests
+are failing.
+
+
+### Code of conduct
+
+We expect all our contributors to follow the [code of
+conduct](CODE_OF_CONDUCT.md).

README.md

@@ -157,6 +157,10 @@ All Docker images support arm64 and amd64 architectures.
 For a full list of tags, including versioned images, see
 https://hub.docker.com/u/dolfinx
 
+## Contributing
+
+Information about how to contribute to DOLFINx can be found
+[here](CONTRIBUTING.md).
 
 ## License