add help button for how to pop out video in firefox

[jwunderl]

Possible quick fix for microsoft/pxt-arcade#5490, since firefox doesn't support picture in picture api / have there own way to do it.

We'd have to write a quick markdown page at /firefox-picture-in-picture which I didn't do, but would likely largely be similar to https://support.mozilla.org/en-US/kb/about-picture-picture-firefox

[thsparks]

LGTM, but should we wait until we have the docs to check in?

[kiki-lee]

Could we do an anigif to quickly show how instead? Something that appears in a div when you click that button?

[abchatra]

Primary object for the students is to watch the video and popping out is secondary action only if required. This long text makes me think, students will try to click or play with the button instead of watching the video. Just keep the old "Pop out" and take them to the documentation page for firefox? It is also not worthwhile to spending engineering effort on this as Firefox is less than 1% of our use base.

[jwunderl]

Yeah, I'd prefer to just leave it as linking out to md page vs injecting a gif; in addition to time constraints also think we'd want more troubleshooting info (e.g. how to reenable the feature if it's off in settings for whatever reason, instructions that can be read for accessibility, potential contrast issues, confusion from a gif just popping up instead of what they expected)

[kiki-lee]

I'm kind of worried that the pop-out markdown would cause more trouble than the video. Even with the button, they're probably pretty likely to click that full-screen icon.

This is a tough one,