Add a filler node for VoiceOver to VideoContext

[emettely]

Is your feature request related to a problem? Please describe.
#65

Describe the solution you'd like

https://github.com/bbc/VideoContext
Add a node (of your choice) to the videocontext to be able to see the voiceover in the rough cut video.

Describe alternatives you've considered
See ADR #65

Additional context