Improve the grammar of messages about GPX and KML files (#6497)

Add articles, fix capitalization, add ellipses.

Author: amire80

app/src/main/res/values/strings.xml

@@ -827,12 +827,12 @@ Upload your first media by tapping on the add button.</string>
   <string name="invalid_login_message">Your log-in has expired. Please log in again.</string>
   <string name="no_application_available_to_open_gpx_files">No application available to open GPX files</string>
   <string name="file_saved_successfully">File Saved Successfully</string>
-  <string name="do_you_want_to_open_gpx_file">Do you want to open GPX file?</string>
-  <string name="do_you_want_to_open_kml_file">Do you want to open KML file?</string>
-  <string name="failed_to_save_kml_file">Failed to save KML file.</string>
-  <string name="failed_to_save_gpx_file">Failed to save GPX file.</string>
-  <string name="saving_kml_file">Saving KML File</string>
-  <string name="saving_gpx_file">Saving GPX File</string>
+  <string name="do_you_want_to_open_gpx_file">Do you want to open the GPX file?</string>
+  <string name="do_you_want_to_open_kml_file">Do you want to open the KML file?</string>
+  <string name="failed_to_save_kml_file">Failed to save the KML file.</string>
+  <string name="failed_to_save_gpx_file">Failed to save the GPX file.</string>
+  <string name="saving_kml_file">Saving as a KML file...</string>
+  <string name="saving_gpx_file">Saving as a GPX file...</string>
   <plurals name="custom_picker_images_selected_title_appendix">
     <item quantity="one">%d image selected</item>
     <item quantity="other">%d images selected</item>