DOC: add migration guidelines (#191)

Co-authored-by: Revathy Venugopal <[email protected]>

Author: jorgepiloto

doc-deploy-dev/action.yml

@@ -1,11 +1,18 @@
 name: >
   Doc deploy dev action
 
-description: >
+description: |
   This action deploys the desired HTML documentation artifact containing the
   development version of a library to the specified branch of a repository. By
   default, the ``gh-pages`` branch of the current repository is assumed.
 
+  .. note::
+
+      If your project is using ``pyansys/actions@v3`` or lower and you would
+      like to update to this version of the actions, see the `guidelines for
+      migrating to the latest multi-version documentation layout
+      <https://dev.docs.pyansys.com/how-to/documenting/multi-version-migration-from-pyansys-actions-v3-to-pyansys-actions-v4>`_ .
+
 inputs:
 
   # Required inputs

doc-deploy-stable/action.yml

@@ -1,11 +1,18 @@
 name: >
   Doc deploy stable action
 
-description: >
+description: |
   This action deploys the desired HTML documentation artifact containing the
   stable version of a library to the specified branch of a repository. By
   default, the ``gh-pages`` branch of the current repository is assumed.
 
+  .. note::
+
+      If your project is using ``pyansys/actions@v3`` or lower and you would
+      like to update to this version of the actions, see the `guidelines for
+      migrating to the latest multi-version documentation layout
+      <https://dev.docs.pyansys.com/how-to/documenting/multi-version-migration-from-pyansys-actions-v3-to-pyansys-actions-v4>`_ .
+
 inputs:
 
   # Required inputs