FEATURE: 378463
Add '%T' placeholder for filename pattern to insert window title.
Example filenames for pattern `%Y-%M-%D %H-%m-%S. %T`:
2018-02-21 19-10-421-55. Full screenromas : byobu.png
2018-02-21 19-11-03. Desktop.png2-20.png
Example filenames for pattern `%T`:
2018-02-21 19-11-55. romas : byobu.png
2018-02-21 19-12-20. RegionScreenshot.png