Problem: invalid link in README.md

[stephan57160]

Seen in this README.md :

Specification lifecycle SHOULD follow the lifecycle defined in [COSS](http://rfc.unprotocols.org/spec:2/COSS)

The COSS link leads to "page not found".

[justusranvier]

I found a copy of that specification using the Wayback Machine:

https://web.archive.org/web/20190326050037/https://rfc.unprotocols.org/spec:2/COSS/