Update flatpak description

org.opennumismat.OpenNumismat.metainfo.xml

@@ -2,10 +2,11 @@
 <component type="desktop-application">
   <id>org.opennumismat.OpenNumismat</id>
   <name>OpenNumismat</name>
-  <summary>Collecting software for organize and manage your own catalogue</summary>
+  <summary>Custom coin collection catalog</summary>
   <description>
     <p>OpenNumismat is a handy and reliable application aimed at coin collectors, numismatists or amateurs looking to create a numismatics collection.</p>
     <p>With OpenNumismat, you will be able to organize and manage coin collection: create an advanced catalogue of your coins, wish and selling lists, view statistics for your collection.</p>
+    <p>Suitable for other collectibles, like stamps, banknotes, postcards, badges, scale models. And also for organize home inventory.</p>
   </description>
   <metadata_license>FTL</metadata_license>
   <project_license>GPL-3.0-or-later</project_license>
@@ -16,17 +17,21 @@
   <screenshots>
     <screenshot type="default">
       <caption>Main window</caption>
-      <image>http://opennumismat.github.io/images/screenMain.png</image>
+      <image>https://opennumismat.github.io/images/screenMain.png</image>
     </screenshot>
     <screenshot>
       <caption>Edit dialog</caption>
-      <image>http://opennumismat.github.io/images/screenEdit.png</image>
+      <image>https://opennumismat.github.io/images/screenEdit.png</image>
     </screenshot>
     <screenshot>
       <caption>Statistics chart</caption>
-      <image>http://opennumismat.github.io/images/screenStatistics4.png</image>
+      <image>https://opennumismat.github.io/images/screenStatistics4.png</image>
     </screenshot>
   </screenshots>
+  <branding>
+    <color type="primary" scheme_preference="light">#fef5be</color>
+    <color type="primary" scheme_preference="dark">#423400</color>
+  </branding>
   <developer id="opennumismat.org">
     <name>Janis</name>
   </developer>