add missing icons, cleanup translations, fix last little issues, prepare for documentation

resources/li.sopht.Flashcards.metainfo.xml.in

@@ -6,9 +6,6 @@
 
   <name>Flashcards</name>
   <summary>Learn categories with flashcards!</summary>
-  <description>
-    <p>No description</p>
-  </description>
 
   <developer id="li.sopht">
     <name translate="no">Sophie Krause</name>
@@ -38,13 +35,6 @@
     <color type="primary" scheme_preference="dark">#993d3d</color>
   </branding>
 
-  <screenshots>
-    <screenshot type="default">
-      <image>https://example.org/example1.png</image>
-      <caption>A caption</caption>
-    </screenshot>
-  </screenshots>
-
   <releases>
     <release version="1.0.0" date="2025-02-18">
     </release>