docs: add `CONTRIBUTING.MD`

CONTRIBUTING.md

@@ -0,0 +1,10 @@
+# Contributing
+
+If you open a PR please consider the following:
+
+- If you're adding new functionality, please open an issue to discuss the design of the new feature
+- How the end user will consume your new feature. It's often easier to start with the API and work backwards
+- Consider the use of [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/) to make your commit messages more descriptive
+- Add new tests to the plugin (use the existing ones as a template)
+
+The mantra for this plugin is "simple session management" and as such the code base is relatively simple. Please consider this in your code.