Explain the 'link to timecode' feature

[squiddy]

We landed the timecode feature (#89) that allows users to link to a video at a specific time position. However, we're currently not explaining that this feature exists and how to use it. We need to figure out a good way to do this.

Options include:

• a help system focused on site visitors
• context-sensitive help (e.g. [?] at places with non-obvious usage)