[IMP] website_form: make adding a field to the form clearer

This commit adds a label next to the + icon and uses a primary button to
make adding a field clearer.

Part of https://github.com/odoo/odoo/pull/72180
task-2566338

addons/website_form/views/snippets/s_website_form.xml

@@ -48,21 +48,21 @@
 
         <!-- Add Field Form -->
         <div data-js="AddFieldForm" data-selector=".s_website_form" data-target="form">
-            <we-button class="o_we_text_success"
+            <we-button class="o_we_bg_brand_primary"
                 title="Add a new field at the end"
                 data-add-field=""
                 data-no-preview="true">
-                <i class="fa fa-fw fa-plus"/>
+                + Field
             </we-button>
         </div>
 
         <!-- Add Field -->
         <div data-js="AddField" data-selector=".s_website_form_field" data-exclude=".s_website_form_dnone">
-            <we-button class="o_we_text_success"
+            <we-button class="o_we_bg_brand_primary"
                 title="Add a new field after this one"
                 data-add-field=""
                 data-no-preview="true">
-                <i class="fa fa-fw fa-plus"/>
+                + Field
             </we-button>
         </div>