Add contributing guidelines

CONTRIBUTING.md

@@ -0,0 +1,31 @@
+# Contributing
+
+The following is a set of guidelines for contributing to `res2df`.
+
+There are several important ways you can help; here are some examples:
+
+- Submitting bug reports and feature requests: see [Issues](https://github.com/equinor/res2df/issues).
+- Proposing code for bug fixes and new features, then [making a pull request](https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests).
+- Fixing typos and generally improving the documentation.
+- Writing tutorials, examples, and how-to documents.
+
+
+## Commits
+
+We strive to keep a consistent and clean git history and all contributions should adhere to the following:
+
+1. All tests should pass on all commits
+1. A commit should do one atomic change on the repository
+1. The commit headline should be descriptive and in the imperative
+
+Please note that we use [`black`](https://black.readthedocs.io/en/stable/) and [`isort`](https://pycqa.github.io/isort/) for code formatting.
+
+
+## Pull request process
+
+1. Work on your own fork of the main repo.
+1. Push your commits and make a draft pull request using the pull request template.
+1. Check that your pull request passes all tests.
+1. When all tests have passed and your are happy with your changes, change your pull request to "ready for review", and ask for a code review.
+1. When your code has been approved you should rebase, squash and merge your changes.
+