Freedesktop: Adding missing appdata.xml file (AppStream-XML)

It provides metadata for app stores like KDE's Discover or the Gnome Store.
The info inside this file can be improved. It has been quickly generated with a generator made by the Freedesktop people.

Signed-off-by: Thomas Karl Pietrowski <thopiekar@gmail.com>

CMakeLists.txt

@@ -206,6 +206,9 @@ install(
     DESTINATION ${CMAKE_INSTALL_DATADIR}/icons/hicolor/128x128/apps/
     RENAME org.mavlink.qgroundcontrol.png
 )
+install(
+    FILES ${CMAKE_SOURCE_DIR}/deploy/org.mavlink.qgroundcontrol.metainfo.xml
+    DESTINATION ${CMAKE_INSTALL_DATADIR}/metainfo/
 )
 
 if(BUILD_TESTING)

deploy/org.mavlink.qgroundcontrol.metainfo.xml

@@ -0,0 +1,39 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<component type="desktop-application">
+  <id>org.mavlink.qgroundcontrol</id>
+  
+  <name>QGroundControl</name>
+  <summary>UAS ground control station</summary>
+  
+  <metadata_license>MIT</metadata_license>
+  <project_license>GPL-3.0-only</project_license>
+  
+  <recommends>
+    <control>pointing</control>
+    <control>keyboard</control>
+    <control>touch</control>
+    <control>gamepad</control>
+  </recommends>
+  
+  <description>
+    <p>
+      Intuitive and Powerful Ground Control Station for the MAVLink protocol.
+    </p>
+  </description>
+  
+  <launchable type="desktop-id">org.mavlink.qgroundcontrol.desktop</launchable>
+  <screenshots>
+    <screenshot type="default">
+      <image>https://docs.qgroundcontrol.com/assets/quickstart/ConnectedVehicle.jpg</image>
+    </screenshot>
+  </screenshots>
+  
+  <categories>
+    <category>Utility</category>
+    <category>Maps</category>
+  </categories>
+  
+  <provides>
+    <binary>QGroundControl</binary>
+  </provides>
+</component>