DOC: Updates to contribution guide

Updates to the contribution guide in preparation for the hack session.

Principal changes are the addition of ## Unit Testing, and modifications to the description of commit messages to reflect adoption of scipy standard

containers/env-template.yml

@@ -69,6 +69,7 @@ dependencies:
   - nbconvert
   - twine
   - glasflow
+  - myst_parser
   - pip:
     - autodoc
     - ipykernel