JPG Placeholder - self-hosted placeholder images (svg/png)
usage: GET /{width}[x{height}][@{2x|3x}][.{svg|png}][?text=...][&bg=...][&fg=...]
e.g.   GET /600x400 /600x400.png /600x400@2x?text=Hello&bg=cccccc&fg=333333
limits: 10..4000 px per side, 2x/3x retina, caption up to 200 chars