docs(multi): add auto configuration variable

docs/tutorial/index.rst

@@ -57,4 +57,5 @@ Let's dive into this **configuration options validation** use case.
    jinja
    customtype
    nullable
+   multiple
    whatsnext

docs/tutorial/multiple.rst

@@ -0,0 +1,56 @@
+Variable with multiple values
+================================
+
+.. objectives:: Objectives
+
+   FIXME
+
+.. prerequisites:: Prerequisites
+
+    - We assume that Rougail's library is :ref:`installed <installation>` on your computer.
+
+    - It is possible to retrieve the current state of the various Rougail files manipulated in this tutorial step
+      by checking out the corresponding tag of the `rougail-tutorials` git repository.
+      Each tag corresponds to a stage of progress in the tutorial.
+      Of course, you can also decide to copy/paste or download the tutorial files contents while following the tutorial steps.
+
+    If you want to follow this tutorial with the help of the corresponding :tutorial:`rougail-tutorials git repository <src/branch/v1.1>`,
+    this workshop page corresponds to the tags :tutorial:`v1.1_100 <src/tag/v1.1_100/README.md>` to :tutorial:`v1.1_111 <src/tag/v1.1_111/README.md>`
+    in the repository.
+
+    ::
+
+       git clone https://forge.cloud.silique.fr/stove/rougail-tutorials.git
+       git switch --detach v1.1_100
+
+.. type-along:: A web_address variable
+
+A conditional disabled variable with type web_address
+-------------------------------------------------------------
+
+Fist we need to add a variable as part of our use case with a type we haven't used yet, the `web_address` type.
+It is related to the automatic proxy configuration situation. 
+Let's put it a new :file:`firefox/30-auto.yml` :term:`structure file`. 
+Note that this variable has a :term:`disabled` property defined:
+
+.. extinclude:: https://forge.cloud.silique.fr/stove/rougail-tutorials/raw/commit/v1.1_100/firefox/30-auto.yml
+   :language: yaml
+   :caption: The :file:`firefox/30-auto.yml` structure definition file with the `auto` variable
+
+.. 
+    %YAML 1.2
+    ---
+    version: 1.1
+
+    auto:
+      description: Automatic proxy configuration URL
+      type: web_address
+      disabled:
+        variable: _.proxy_mode
+        when_not: Automatic proxy configuration URL
+    ...
+    
+If the `proxy_mode` variable has the `"Automatic proxy configuration URL"` value, this `auto` variable is enabled.
+It is :term:`disabled` otherwise.
+
+