Storage for large files, such as MP4s

As we embed more videos and MP4 files in our docs, we need to be able to store these large files in Github.

Requirements:

- The ability to store the original source files so that if something happens to our laptops, the original files are safe.
- When a repo is cloned, there should be an option to deselect the large visual files so that cloning doesn't take too long.

This issue does not include the Education team videos, such as [this Discover video](https://www.elastic.co/guide/en/kibana/current/discover.html), which are separately managed and maintained.