[IMP] website[_event,_sale]: add plausible as Analytics solution

This commit add the way to specify the Plausible shared key auth token and
the plausible domain on your website to have the Plausible Dashboard integrated
in your Website > Dashboard > Analytics menu.

Some custom event are already pre-configured as:

Push an event 'Shop' on confirmation on ecommerce (with amount bucket +/- 50)
Push an event 'Lead Generation' on:
    'Thank you' page of contactus
    Confirmation of subscription for an event

From this way, the end user can just add a goal 'Lead Generation'
or 'Shop' on Plausible to have the Goal values visible.

closes odoo/odoo#91058

Related: odoo/documentation#2007
Signed-off-by: Romain Derie (rde) <rde@odoo.com>

addons/website/data/website_data.xml

@@ -189,6 +189,7 @@
                             </div>
                         </section>
                     </div>
+                    <input t-if='website.plausible_shared_key' type='hidden' class='js_plausible_push' data-event-name='Lead Generation' data-event-params='{"CTA": "Contact Us"}' />
                 </t>
             </t>
         </field>