In using `:video`, removes the requirement that URL must start with https (in `makeVideoHtml()`)

[cedricsam]

(redoing https://github.com/newsdev/ai2html/pull/179 because i had to make a separate PR/suggestion!)

• Could be useful for videos hosted at a relative URL or for URL rewriting (let's say you're on staging and want to point to a video on staging server; then switch to live seamlessly)

• I could also see a case where the .mp4 check could be removed but that seems like most people will support at least mp4 and can rewrite it if they're in an environment that allows JS