update some testing configs

[squarebracket]

• bump karma browser runners versions
• make detect-browsers' postDetection fancier
• don't remove safari from available browsers
• align some karma settings with VHS
• mute playback tests (which means chrome won't block autoplay)
• dockerize it
• use latest firefox
• bump detect-browsers so we can use preferHeadless: true option instead of manually rewriting that we want a headless browser
• be fancier with Chrome customLaunchers

[squarebracket]

Made appropriate changes, plus a couple little other ones. For some reason, on my test mac, but not on other platforms, chrome won't let autoplay happen with

this.player = videojs(video, {muted: true});

but does let it happen with

this.player = videojs(video);
this.player.muted(true);

which confuses me greatly, but hey, that it makes it work, so..... :man_shrugging:

[squarebracket]

Err, the package-lock wasn't updated, so that will probably have to be done.