Make events findable by transcript (ideally jump to timestamp)

[LukasKalbertodt]

A really nice feature of ETH's current video portal is that you can search for parts of a transcript. It then shows you videos where your search term was said and also has a visualization when in the video it was said. If you click on the search result, you can directly jump to the timestamp when it was said.

We want that in Tobira as well! Several areas are involved here. First we need the transcription data with timestamps from Opencast. Then we need to put those into Meilisearch. And finally, our frontend needs to display those search results.

Blocked on:

• Add GET parameter to specify a timestamp for a video (e.g. t=3m12s) #191
• Vastly improve frontend-part of the search (current one is only "proof of concept") #620