this is a spin-off of #194 primarily dedicated to fonts.
Let's keep here (an updated) list of fonts publicly available to download and use as seeds.
for freetype, harfbuzz, ots, woff2, etc.

Also let's make sure oss-fuzz actually uses these fonts.

https://github.com/unicode-org/text-rendering-tests
https://github.com/google/fonts
https://github.com/adobe-fonts/ (several repos)

@behdad