[ADD] websites: add plausible.io Dashboard documentation

closes odoo/documentation#2007

Related: odoo/odoo#91058
Signed-off-by: Antoine Vandevenne (anv) <anv@odoo.com>

content/applications/websites/website/optimize.rst

@@ -10,6 +10,7 @@ Optimize
    optimize/seo
    optimize/google_analytics
    optimize/google_analytics_dashboard
+   optimize/plausible
    optimize/link_tracker
    optimize/unsplash
 

content/applications/websites/website/optimize/plausible.rst

@@ -0,0 +1,42 @@
+=====================================================
+How to track your website's traffic with Plausible.io
+=====================================================
+
+To follow your website's traffic with Plausible.io:
+
+- `Create a Plausible.io account <https://plausible.io/register/>`__ if you don't have any.
+
+- `Create your website <https://plausible.io/sites/new/>`__ and `Start collecting data` if it is not already done.
+
+- Go through the `list of your websites <https://plausible.io/sites/>`__ and click on the gear icon.
+
+    .. image:: media/plausible_cog.png
+       :align: center
+
+- Click on the button `+ New Link` in the tab Visibility to create your Shared links.
+
+    .. image:: media/plausible_new_sharedlink.png
+       :align: center
+
+- Choose a name (and NO password - it is not supported to embed it in Odoo) and click on the button `Create Shared Link`
+
+    .. image:: media/plausible_create_sharedlink.png
+       :align: center
+
+- Copy the new Shared Link url from Plausible.io and paste it in the Settings of Odoo
+
+    .. image:: media/plausible_copy_sharedlink.png
+       :align: center
+    .. image:: media/plausible_paste_sharedlink.png
+       :align: center
+
+
+.. note:: You are on the Odoo Saas Platform?
+
+    When you `create your database on www.odoo.com/trial <https://www.odoo.com/trial>`__, we create it for you on our own server.
+    You don't have anything to do.
+
+
+.. note:: What about the Goal?
+
+    Odoo push out-of-the-box some custom event: `Lead Generation` and `Shop`.