Add docs for the tempest-k8s charm

Change-Id: I7d5538c74bb28e9c9a78235aaec76d23a09c4e40

charms/tempest-k8s/CONTRIBUTING.md

@@ -11,9 +11,14 @@ Please see the tox.ini file in the root of this repository.
 For example:
 
 ```
+# Autoformat the code according to the project's guidelines
 tox -e fmt
+
+# Run linters on the code
 tox -e pep8
-tox -e cover
+
+# Run the unit tests with code coverage
+tox -e cover -- tempest-k8s
 ```
 
 ## Build the charm

charms/tempest-k8s/README.md

@@ -17,4 +17,4 @@ OpenStack deployment.
 
 ## Other resources
 
-- [tempest-k8s](https://charmhub.io/tempest-k8s) on Charmhub
+- [tempest-k8s](https://charmhub.io/tempest-k8s) on Charmhub (more docs there)

charms/tempest-k8s/charmcraft.yaml

@@ -44,6 +44,7 @@ assumes:
 links:
   source: https://opendev.org/openstack/sunbeam-charms
   issues: https://bugs.launchpad.net/sunbeam-charms
+  documentation: https://discourse.charmhub.io/t/tempest-k8s-docs-index/13258
 
 containers:
   tempest: