Add characters per second (CPS) count
One nice feature of Aegisub and Subtitle Workshop was the count for Characters Per Second (CPS).
This varies according to language and is described in many subtitling guidelines, among them Netflix (20 chars per second) and BBC.
Some more in-depth info about this feature can be found here: https://www.proz.com/forum/subtitling/281639-cps_settings_with_aegisub.html
This is relevant to ensure the person reading the subtitles is able to follow it properly.
It would be nice if it followed the changing colors suggested in #33 (closed), and generally speaking just a counter for that would be fine too.