Support pausing timer on handlePauseRecording call

[AlaDouagi]

The pause/resume recording features (triggered using component refs) are poorly supported, for instance, the timer keeps counting even after pausing the recording, and currently there is no way to manipulate the recording timer outside of the react-video-recorder component so I can bypass the problem, after quickly checking the source code it seems that the pause recording functionality isn't being considered at all, the <Timer /> component just keeps incrementing when it exists and it will disappear when isRecording is falsy. I will try to check this problem and maybe open a PR when I get some free time.