[gnome-maps] exportViewDialog: Add translator comment for filename template

[Marcus Lundblad <mlundblad src gnome org>]

commit e73f97ed981d4811a350df8af53c6a3fd91af689
Author: Marcus Lundblad <ml update uu se>
Date:   Thu Oct 12 23:12:17 2017 +0200

    exportViewDialog: Add translator comment for filename template

 src/exportViewDialog.js |    4 ++++
 1 files changed, 4 insertions(+), 0 deletions(-)
---
diff --git a/src/exportViewDialog.js b/src/exportViewDialog.js
index 2264dd1..a18bf2a 100644
--- a/src/exportViewDialog.js
+++ b/src/exportViewDialog.js
@@ -82,6 +82,10 @@ var ExportViewDialog = new Lang.Class({
     },
 
     _getName: function() {
+        /* Translators: This is a format string for a PNG filename for an
+         * exported image with coordinates. The .png extension should be kept
+         * intact in the translated string.
+         */
         return _("Maps at %f, %f.png").format(this._latitude.toFixed(2),
                                               this._longitude.toFixed(2));
     },