Create initial CONTRIBUTING.md (#26)

* docs: Update wording to reflect project state. Keeping it simple.

Signed-off-by: Peter Fiddes <peter.fiddes@jestack.io>

Author: hawksight

CONTRIBUTING.md

@@ -0,0 +1,15 @@
+# Contributing to this project
+
+This project is new and supported on a best efforts basis.
+We welcome contributions but cannot set any expectations for response, review or acceptance.
+
+## Issues & Features
+
+Please use the repository [issues](https://github.com/jetstack/terraform-provider-tlspc/issues) for raising bugs and feature requests.
+
+## Contributions
+
+1. Fork the project and work on a branch.
+1. Ensure to sign off your commits using `git commit --signoff` option.
+1. Raise a Pull Request back to this repository for review.
+1. Please be patient with the team.