Add contribution guidelines

CONTRIBUTING.md

@@ -0,0 +1,18 @@
+# Contributing
+
+If you'd like to contribute to CabanaPD, please open a [pull
+request](https://help.github.com/articles/using-pull-requests/) with
+`main` as the destination branch on the
+[repository](https://github.com/ORNL/CabanaPD) and allow edits from
+maintainers in the pull request.
+
+Your pull request must pass tests, which includes using the coding
+style from `.clang-format` (enforced with clang-format-14), and be
+reviewed by at least one CabanaPD developer. Formatting can be applied
+with `make format` within the build folder.
+
+`pre-commit` is a useful tool for ensuring feature branches are ready for
+review by running automatic checks locally before a commit is made.
+[Installation details](https://pre-commit.com/#install) (once per system) and
+[activation details](https://pre-commit.com/#usage) (once per repo) are
+available.

README.md

@@ -138,6 +138,11 @@ loading, in Impact Loading and Dynamic Behavior of Materials, C.Y. Chiem, H.-D.
 Kunze, and L.W. Meyer, eds., Vol 1, DGM Informationsgesellschaft Verlag (1988)
 185-195.
 
+## Contributing
+
+We encourage you to contribute to CabanaPD! Please check the
+[guidelines](CONTRIBUTING.md) on how to do so.
+
 ## Citing CabanaPD
 
 If you use CabanaPD in your work, please cite the [Zenodo release](https://zenodo.org/record/7087781#.Y309w7LMLKI).