Adding presentation videos is very error prone (and "talks" page is too complex to edit)

[jtattermusch]

Adding new content to the page should be easy, but instead one needs to edit two different files, for the video player to work correctly and that's extremely easy to miss.

Example:
See issue #797 (introduced by #730 which didn't update the .js file which broke the player for a long period of time).

Also, they tile layout of the video thumbnails is currently broken (see https://grpc.io/docs/talks/) and I wasn't able to fix that after spending non-trivial amount of time trying to do so. Such complexity (all the CSS, javascript etc.), really asks for simplification. I shouldn't need to spend hours on trying to add a presentation video.