XdgAppError: Add documentation

lib/xdg-app-error.c

@@ -25,4 +25,10 @@
 
 #include <gio/gio.h>
 
+/**
+ * SECTION:xdg-app-error
+ * @Title: Error codes
+ *
+ */
+
 G_DEFINE_QUARK (xdg-app-error-quark, g_io_error)

lib/xdg-app-error.h

@@ -30,6 +30,8 @@ G_BEGIN_DECLS
  * XdgAppError:
  * @XDG_APP_ERROR_ALREADY_INSTALLED: App/runtime is already installed
  * @XDG_APP_ERROR_NOT_INSTALLED: App/runtime is not installed
+ *
+ * Error codes for library functions.
  */
 typedef enum {
   XDG_APP_ERROR_ALREADY_INSTALLED,