updated appdata

Author: mdh34

data/com.github.mdh34.quickdocs.appdata.xml

@@ -49,6 +49,12 @@
     <screenshot>
       <image>https://raw.githubusercontent.com/mdh34/quickDocs/master/data/images/screenshot-2.png</image>
     </screenshot>
+    <screenshot>
+      <image>https://raw.githubusercontent.com/mdh34/quickDocs/master/data/images/screenshot-3.png</image>
+    </screenshot>
+    <screenshot>
+      <image>https://raw.githubusercontent.com/mdh34/quickDocs/master/data/images/screenshot-4.png</image>
+    </screenshot>
   </screenshots>
   <custom>
     <value key="x-appcenter-color-primary">#b972b7</value>