Generate thumbnails (sequence of preview images) for online videos
This will only work for standard video player. Where video source url can be found in video or its child elements. For example YouTube's videos not supported.
How to use:
1. Click extension's icon and then 'enable for this website'
2. Move your cursor over target video and wait for a few seconds
3. Thumbnails will be ready when you see notification 'Thumbnails ready!'
4. Click that notification and you'll see your images. Alternatively open popup and click one of thumbnails that you made previously.
