data: List compatible form-factors

This lists the form-factors the app was designed for in the AppStream
data and the desktop entry.

data/org.gnome.zbrown.KingsCross-generic.desktop.in

@@ -11,3 +11,4 @@ Categories=System;TerminalEmulator;X-GNOME-Utilities;GTK;GNOME;
 StartupNotify=true
 DBusActivatable=true
 X-GNOME-UsesNotifications=true
+X-Purism-FormFactor=Workstation;Mobile;

data/org.gnome.zbrown.KingsCross.appdata.xml.in

@@ -50,4 +50,8 @@
   <translation type="gettext">kgx</translation>
   <content_rating type="oars-1.1" />
   <developer_name>Zander Brown</developer_name>
+  <custom>
+    <value key="Purism::form_factor">workstation</value>
+    <value key="Purism::form_factor">mobile</value>
+  </custom>
 </component>

data/org.gnome.zbrown.KingsCross.desktop.in

@@ -12,3 +12,4 @@ Categories=System;TerminalEmulator;X-GNOME-Utilities;GTK;GNOME;
 StartupNotify=true
 DBusActivatable=true
 X-GNOME-UsesNotifications=true
+X-Purism-FormFactor=Workstation;Mobile;