appdata: Improve appdata for AppStream 1.0

- Add the `<developer><name>` tag
- Mark the `<developer_name>` tag as deprecated
- Update display_length tag
- Fix screenshot tags
- Update appstreamcli validation

data/com.github.ADBeveridge.Raider.metainfo.xml.in.in

@@ -25,14 +25,17 @@
   <url type="vcs-browser">https://github.com/ADBeveridge/raider/tree/develop</url>
   <url type="translate">https://github.com/ADBeveridge/raider/tree/develop/po</url>
   <update_contact>[email protected]</update_contact>
+  <!-- developer_name tag deprecated with Appstream 1.0 -->
   <developer_name translatable="no">Alan Beveridge</developer_name>
+  <developer id="github.com">
+    <name translatable="no">Alan Beveridge</name>
+  </developer>
   <requires>
-    <display_length compare="ge">small</display_length>
+    <display_length compare="ge">360</display_length>
   </requires>
   <recommends>
     <control>pointing</control>
     <control>keyboard</control>
-    <display_length compare="ge">small</display_length>
   </recommends>
   <supports>
     <control>tablet</control>
@@ -43,6 +46,8 @@
   <screenshots>
     <screenshot type="default">
       <image>https://raw.githubusercontent.com/ADBeveridge/raider/main/data/raider-screenshot1.png</image>
+    </screenshot>
+    <screenshot>
       <image>https://raw.githubusercontent.com/ADBeveridge/raider/main/data/raider-screenshot2.png</image>
     </screenshot>
   </screenshots>