[1.5.X] Fixed #19582 - Added a static files tutorial.

Thanks James Pic.

Backport of c32fc79aa1 from master
[1.5.x] Fixed #19897 - Updated static files howto.

Thanks Jan Murre, Reinout van Rees and Wim Feijen,
plus Remco Wendt for reviewing.

Backport of i6c730da1f from master.