add rel="noopener" to target="_blank" links
add rel="noopener" to target="_blank" links

see: https://mathiasbynens.github.io/rel-noopener/ for more information.

we might also consider rel="noopener noreferrer nofollow", but thats a bit opinionated for a md library (even if i personally would prefer it being used all the time)
Holixus/nanomarkdown,Holixus/nano-markdown