docs: add instructions to contribute to project

CONTRIBUTING.md

@@ -0,0 +1,34 @@
+# Contributing
+
+This project accepts community contributions. In order to contribute, please:
+
+1. Follow the coding style guidelines below
+2. Agree to the Developer Certificate of Origin
+3. Submit a GitHub pull request (PR) for review
+
+## Coding Style
+
+Please make sure to run [Black](https://black.readthedocs.io/en/stable/index.html)
+and [Flake8](https://flake8.pycqa.org/en/latest/) before submitting a PR.
+
+## Developer Certificate of Origin
+
+By contributing a PR to this project you agree to the [Developer Certificate of Origin (DCO)](https://developercertificate.org/).
+
+In short, you agree that you can make the contribution and that the project has
+the right to distribute your contribution under the terms of the project's
+[LICENSE](LICENSE). The PR itself is a sign-off of your agreement to the DCO.
+
+## Submission
+
+Submit a PR against the `main` branch. Please include one of the following
+prefixes in your commit messages so the [CHANGELOG](CHANGELOG.md) can be updated
+automatically:
+
+* `feat:` Adds a new feature
+* `fix:` Fixes a bug in the code
+* `refactor:` Restructures the code without changing its external behavior
+* `docs:` Documentation only changes
+* `test:` Adds or modifies tests
+* `style:` Changes to whitespace, formatting, etc; no code changes
+* `chore:` Changes to the build process or auxiliary tools

README.md

@@ -269,3 +269,9 @@ so these are not part of the official release.
 
 The images are saved as PNGs in the `output` folder using the prompt text. The
 `build.sh` script creates and mounts this folder as a volume in the container.
+
+## Contribution
+
+See the [CONTRIBUTING.md](CONTRIBUTING.md) file for more details. In short,
+follow the style guidelines, agree to the Developer Certificate of Origin, and
+submit a PR.