Adds a link to the mp4 file of gfycat webm, redirects from detail page to actual file page
Add a direct link to the MP4 and WEBM files on gfycat.com and redgifs.com video pages for convenience.
Optionally can redirect after 5 seconds from "details page" to the actual file (with video player) page. But the "details page" doesn't seem to be used anymore anyway (for Gfycat).
The source URL *should* be displayed by gfycat natively now, so that part is now probably obsolete (doesn't really work currently?)
Known issue: the script doesn't work when after clicking "up next" links at the bottom of the page (probably need a promise somewhere).
This script does the same job, but better: https://greasyfork.org/en/scripts/408129-gfycat-show-all-download-links-gif-mp4-webp-webm
