Better video embedding - Part 2

Due to many requests from our users we have changed how video embedding works.

Now, video player is not loaded automatically when you open the page, but only after you click on the video thumbnail.

This has two consequences:

1. Better performance - since player is not loaded when page starts, your device can focus on rendering rest of the note
2. Better privacy - since external player is loaded only to those who click on the thumbnail

You can see how embedding video works by putting YouTube video URL in separate line, e.g. https://www.youtube.com/watch?v=k6ZoE4RrcDs

Another positive change is that now video thumbnails will be visible on generated PDF files.