Add Support for a Blockchain | Ceramic documentation

The standard use of SIWX, CACAO and DID:PKH allows anyone to implement support for another blockchain or account type to authenticate and authorize writes to the Ceramic Network. Additionally a few standard interfaces enables you to implement an auth and verification library that allows anyone to use it with did-session, the primary library to use DID based accounts with Ceramic. There is just a few steps you have to take, outlined below.