[gnome-software: 1/3] docs: Add an XML example on the vendor-customisation.md page

[Philip Withnall <pwithnall src gnome org>]

commit b0bc63231956334ff4546677792719eada70a6c8
Author: Philip Withnall <pwithnall endlessos org>
Date:   Wed Apr 6 12:23:34 2022 +0100

    docs: Add an XML example on the vendor-customisation.md page
    
    This should clarify the XML needed to feature an app.
    
    Signed-off-by: Philip Withnall <pwithnall endlessos org>

 doc/vendor-customisation.md | 35 +++++++++++++++++++++++++++++++++++
 1 file changed, 35 insertions(+)
---
diff --git a/doc/vendor-customisation.md b/doc/vendor-customisation.md
index 9e8b556a9..24f182df8 100644
--- a/doc/vendor-customisation.md
+++ b/doc/vendor-customisation.md
@@ -109,6 +109,41 @@ sections:
    meet the requirements for being in the carousel, but weren’t chosen as part
    of the randomisation process.
 
+Example:
+```xml
+<?xml version="1.0" encoding="UTF-8"?>
+<components>
+  <component merge="append">
+    <!-- The ID must always be present to allow merging -->
+    <id>org.gnome.Podcasts</id>
+
+    <!-- Make the app a candidate for inclusion in the carousel on the
+         overview page (if it has a hi-res icon). -->
+    <custom>
+      <value key="GnomeSoftware::FeatureTile">True</value>
+    </custom>
+
+    <!-- Include the app in the “Editor’s Choice” section on the overview page. -->
+    <kudos>
+      <kudo>GnomeSoftware::popular</kudo>
+    </kudos>
+
+    <!-- Make the app a candidate for inclusion in the carousel or
+         “Editor’s Choice” section on category pages (if it has a hi-res icon). -->
+    <categories>
+      <!-- Note that, due to a bug (https://gitlab.gnome.org/GNOME/gnome-software/-/issues/1649),
+           currently all the other categories for the app must also be listed
+           here, as well as the additional ‘Featured’ category. -->
+      <category>AudioVideo</category>
+      <category>Player</category>
+      <!-- This category has been added: -->
+      <category>Featured</category>
+    </categories>
+  </component>
+  <!-- more components -->
+</components>
+```
+
 There are several ways to modify the metainfo for applications so that they are
 highlighted as required, all of which involve providing an additional appstream
 file which sets the additional metainfo for those applications.