General documentation refinements.

doc/Action/With-post-step.rst

@@ -3,3 +3,31 @@
 with-post-step
 ##############
 
+JavaScript Actions support defining ``pre``, ``pre-if``, ``post`` and ``post-if`` steps, which allow executing steps at
+the beginning or the end of a job, regardless of intermediate steps failing. Unfortunately, those are not available for
+any other Action type.
+
+Action **with-post-step** is a generic JavaScript Action to execute a main command and to set a further command as a
+post step. It allows using the ``post`` feature with scripts written in Bash, Python or any other interpreted language
+available on the environment.
+
+**Example Usage:**
+
+.. code-block:: yaml
+
+   jobs:
+     Image:
+       steps:
+         - ...
+
+         - name: Push container image
+           uses: ./with-post-step
+           with:
+             main: |
+               echo '${{ github.token }}' | docker login ghcr.io -u GitHub-Actions --password-stdin
+               docker push ghcr.io/pytooling/releaser
+             post: docker logout ghcr.io
+
+.. seealso::
+
+   * `actions/runner#1478 <https://github.com/actions/runner/issues/1478>`__.