use libvips as last resort due to risk of OOM; example:
libvips defers to imagemagick for animated avif, and imagemagick
probably does an identify, iterating through each frame, itself
consuming 100+ MiB RAM, which libvips amplifies to 7+ GiB
similar behavior is observed with `identify a.mkv` in a shell
* add readme section on using amazon/aws s3 as storage
* mention http/https confusion caused by incorrectly configured cloudflare
* improve custom-font notes
* docker: ftp-server howto
* docker: suggest moving hist-folders into the config path
and switch the idp docker-compose files to use the
main image, in anticipation of v1.11
ed