#1664 add LENGTH column to 7-Zip File Manager

[Eric Ching]

In 7-Zip File Manager please add LENGTH as one of the available column heading fields.

If you have a directory of video files, the LENGTH column field would show the time length
of each of the video files. Beats having to play each file to see how long the video is.
You can easily do this in Windows File Explorer, but it would be nice to do this in 7-Zip as well.

Thanks!