Add IELM screencast

Screencast reference
https://gist.github.com/dergachev/4627207
Use -ss to start at 1 sec
--delay=7 for slower speed gif animation
$ ffmpeg -i ielm.mov -pix_fmt rgb24 -r 10 -f gif -ss 1 - | gifsicle --optimize=3 --delay=7 > out.gif

Use Mousepose for showing keys