h5p/h5p-interactive-video ? reverse-engineered prompt

Build me an H5P interactive video library where authors can add text, questions, and other media on top of a video at specific times.

I want it to feel like a normal H5P content type, so it should have an editor for setting up overlays and tasks, and a player that shows them at the right moments while the video is playing. Make sure it works well inside the H5P ecosystem, with the usual metadata, semantics, language files, upgrades, and build output that can be packed into an H5P library.

Use the existing project structure if it helps, and make the code easy to build and test locally. If you need to check anything about H5P best practices or current docs, look them up online.