record-progress event for Record plugin

[aantusahaa]

Hi,
Foremost, I want to thank you for this awesome library! I primarily use wavesurfer.js for Visualization and the Record plugin.
In the recording portion, I want to show the current progress of the recording in the UI. But right now there is no straight forward way of getting the time from the plugin. I have found this similar discussion. But it doesn't really help me because my case also involves pause and resume of recording.

If we have an event namely record-progress similar to the audioprocess event of wavesurfer itself, we will be able to get that information easily. On a related note, having methods like getCurrentTime(), getDuration() might also be helpful.

[katspaugh]

Those are all good points! I'll happily review a PR and help in case of any questions.

[aantusahaa]

I will try to give it a shot!