[feature request] include cache at progress bar
Can we have progress bar including cache info like mpv ?

This was more annoying to do than I thought since demuxer-cache-state can't easily watched for changes. mpvObject.demuxerCacheState['fw-bytes'] in the playback info Tab seems to update with the current bytes fine, but the embedded seekable-ranges array inside the demuxer-cache-state doesn't seem to change.
- https://mpv.io/manual/master/#command-interface-demuxer-cache-state
I worked around the problem by just watching the demuxerCacheDuration containing the number of seconds of cache left for changes and redrew the cache overlay highlight.

Note to self, the "active cache range" is always the first entry in seekable-ranges.
Thanks !
Cache bar is not accurate, i am not able to skip cached area most of the time.
