[create] Contributing.md

CONTRIBUTING.md

@@ -0,0 +1,20 @@
+# Contributing to swhkd
+
+1. Fork the repo and create your branch from `main`.
+1. Make sure to write tests for the functions you make.
+1. Run `make check` once you're done and ensure the test suite passes.
+
+## Any contributions you make will be under the BSD-2-Clause Software License
+In short, when you submit code changes, your submissions are understood to be under the same BSD-2-Clause License that covers the project. Feel free to contact the maintainers if that's a concern.
+
+## Use a Consistent Coding Style
+I'm again borrowing these from [Facebook's Guidelines](https://github.com/facebook/draft-js/blob/a9316a723f9e918afde44dea68b5f9f39b7d9b00/CONTRIBUTING.md)
+
+* 4 spaces for indentation.
+* You can run `make check` for style unification.
+
+## License
+By contributing, you agree that your contributions will be licensed under its BSD-2-Clause License.
+
+## References
+This document was adapted from [GitHub Gist](https://gist.github.com/briandk/3d2e8b3ec8daf5a27a62).