Added contributions directory.

contributions/README.md

@@ -0,0 +1,9 @@
+# Contributions
+
+This directory contains contributions from the community that may be
+useful to other groups. A good example of a useful contribution are
+file-type conversions.
+
+If you want to contribute something to this repository, please post a
+pull request. If you want to learn more about pull requests you can
+visit the github documentation [here](https://docs.github.com/en/github/collaborating-with-pull-requests/proposing-changes-to-your-work-with-pull-requests/about-pull-requests).