Explore how filmstrip timestamps are generated for telescoptest-io filmstrip -- ADDITION: also explore how filmstrip/video matches the screen

From working on telescopetest-io's filmstrip, I think the numbering of filmstrip frames in telescope need to be altered/given more info in order to be properly timestamped in telescopetest-io's filmstrip display. Right now, the only information that can be used to calculate filmstrip timestamps seems to be `config.json`'s `frameRate`. This makes the filmstrip timestamps slightly off (always a bit over) what the captured video shows.

I think ffmpeg in telescope extracts frames from the captured video? So we either want to number the filmstrip better in telescope or maybe add some total_video_duration value in telescope's output `config.json`.

This would also improve telescope's `--html` option output, which also displays the filmstrip with timestamps (running into same problem).

*EDIT:

Also found this weird instance where the video (and hence filmstrip) doesn't seem to capture the full screen? Or at least the video/filmstrip doesn't capture as much as the screenshot. For example, check the image below. The screenshot captures more of the complete screen than the filmstrip and video:

I checked in R2 for the actual video and filmstrip files, and they're also cropped as shown in the screenshot above. So I don't think it's a telescopetest-io UI issue.