Slideshow/Autoadvance button?

**is your feature request related to a problem? Please describe.**
Enhancement

**Describe the idea / solution you'd like**
Simple slideshow/auto advance button for the media browser.
Similar to #389 but less complicated. Really just the ability to auto advance to the next image in a folder automatically after "x" seconds.

You could also add support for video too, just instead of auto advancing after x seconds the video advances to the next file at the end of playback.

I have people over on occasion and I'd like to be able to give them a link, say "upload all your files here" and once they are done, auto play any images/video they have uploaded.

**Describe any alternatives you've considered**
Looked into solutions in #389, checked doco. also checked out "very-bad-idea" (yeah no)
Presently working around with pointing VLC or Irfanview at the folder after a user uploads everything.

**Additional context**
I get that development time is always at a premium and thank you for everything you've done so far!