fix app metadata and screenshot size

data/org.kuchelmeister.toolbxtuner.appdata.xml.in

@@ -4,6 +4,7 @@
   <id>org.kuchelmeister.toolbxtuner</id>
   <metadata_license>CC0-1.0</metadata_license>
   <project_license>GPL-3.0-or-later</project_license>
+  <content_rating type="oars-1.0" />
   <name>Toolbx Tuner</name>
   <summary>Manage and enhance your toolbxes (containertoolboxes)</summary>
   <description>
@@ -12,20 +13,22 @@
   <screenshots>
     <screenshot type="default">
       <caption>Main application window showing multiple toolboxes</caption>
-      <image type="source" width="1633" height="971">https://media.githubusercontent.com/media/13hannes11/toolbx-tuner/main/data/screenshots/main_light.png</image>
+      <image type="source" width="1200" height="800">https://media.githubusercontent.com/media/13hannes11/toolbx-tuner/main/data/screenshots/main_light.png</image>
     </screenshot>
      <screenshot>
       <caption>Main application window in dark mode</caption>
-      <image type="source" width="1633" height="971">https://media.githubusercontent.com/media/13hannes11/toolbx-tuner/main/data/screenshots/main_dark.png</image>
+      <image type="source" width="1200" height="800">https://media.githubusercontent.com/media/13hannes11/toolbx-tuner/main/data/screenshots/main_dark.png</image>
     </screenshot>
   </screenshots>
-  <content_rating type="oars-1.0" />
+
   <url type="homepage">https://github.com/13hannes11/toolbx-tuner</url>
   <url type="bugtracker">https://github.com/13hannes11/toolbx-tuner/issues/</url>
   <update_contact>hannes_AT_kuchelmeister.org</update_contact>
   <developer_name>Hannes Kuchelmeister</developer_name>
-
   <launchable type="desktop-id">org.kuchelmeister.toolbxtuner.desktop</launchable>
+  <releases>
+    <release version="0.0.0" type="development" date="2022-04-18" />
+  </releases>
 
 </component>