[FIX] theme_*: fix s_text_cover design

This commit has two main goals:

1. Adapt the copy of the `s_text_cover` snippet to fit each theme

2. Introduce custom images for each themes, as the `s_text_cover` was
   always using the same image until now

This commit also fixes some conflicting classes due to a change of
`background-color` in the default snippet.

task-4119904
Part of task-3619705

Part-of: odoo/design-themes#919
Related: odoo/odoo#180736
Signed-off-by: Benjamin Vray (bvr) <bvr@odoo.com>
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

theme_avantgarde/views/customizations.xml

@@ -613,4 +613,19 @@
     </xpath>
 </template>
 
+<!-- ======== TEXT COVER ======== -->
+<template id="s_text_cover" inherit_id="website.s_text_cover">
+    <xpath expr="//h1" position="replace" mode="inner">
+        Design Online. <br/>Effortlessly.
+    </xpath>
+    <!-- Paragraph -->
+    <xpath expr="//p[hasclass('lead')]" position="replace" mode="inner">
+        <br/>Present your architectural projects online with a user-friendly platform that streamlines all the steps, from setup to project showcase, making it easy to share your vision with clients.<br/>
+    </xpath>
+    <!-- Button -->
+    <xpath expr="//a[hasclass('btn')]/t" position="replace" mode="inner">
+        Learn more
+    </xpath>
+</template>
+
 </odoo>

theme_avantgarde/views/images_library.xml

@@ -477,5 +477,10 @@ Check in images.scss, primary_variables.scss, main.scss and theme_common's mixin
     <field name="name">website.s_images_constellation_default_image_2</field>
     <field name="url">/theme_avantgarde/static/src/img/pictures/s_images_constellation_default_image_2.jpg</field>
 </record>
+<record id="s_text_cover_default_image" model="theme.ir.attachment">
+    <field name="key">website.s_text_cover_default_image</field>
+    <field name="name">website.s_text_cover_default_image</field>
+    <field name="url">/theme_avantgarde/static/src/img/pictures/s_text_cover.jpg</field>
+</record>
 
 </odoo>