docs: add hint for verify playbook (#3222)

* docs: add hint for verify playbook

As discussed in #3045, since the `verify.yml` playbook does not run the tested role, the `library` and `module_utils` provided by the tested role are not be available there [1].

Usually, one does not want to re-run the role in the `verify.yml` playbook since it was already run twice before.
One workaround suggested by @tadeboro is to add an empty task list to the role and then to restrict tasks of the role to this file when including it in the `verify.yml` playbook.
This PR adds a note regarding this to the docs.

[1]  (the `library` actually *is* currently available, but [this is an oversight](#3045 (comment)); the `module_utils` are not available.

* Update docs/getting-started.rst

* try fixing linter

* fix linter 2

docs/getting-started.rst

@@ -82,6 +82,27 @@ directories:
   allows you to write specific tests against the state of the container after
   your role has finished executing. Other verifier tools are available (Note that :std:doc:`TestInfra <testinfra:index>` was the default verifier prior to molecule version 3).
 
+.. note::
+
+    If the ``verify.yml`` playbook does not explicitly ``include_role`` your role, the ``library`` and ``module_utils``
+    provided by your role are not available in the playbook by default.
+    If you need those for testing but would like to avoid re-running your role, consider adding
+    an empty task file ``init.yml`` to your role and use ``tasks_from`` to include your role in the ``verify.yml`` playbook:
+
+    .. code-block:: yaml
+
+        - name: Verify
+          hosts: all
+          become: true
+          tasks:
+          - name: Initialize role without actually running it
+            include_role:
+              name: my_role
+              tasks_from: init
+
+          # Start testing: can use role library now
+
+
 .. _Jinja2: http://jinja.pocoo.org/
 
 Inspecting the ``molecule.yml``