Update repo 'about' and Readme

[calmrat]

Please add a short description to this repository which describes it's contents to the repository 'about' section.

eg, "Interface definitions of DDC protocols."

Also, please describe in more detail what the schemas are used for, so it's clear without needing to go to the external documentation to understand.

I suppose the answers are here? https://docs.cere.network/ddc/protocols/contract-params-schema?

The readme should provide the first and most accurate high-level description of the repo's contents. I suggest including release notes should be included here too, first; and in the docs, secondarily (if at all), assuming there is a process for ensuring they remain in sync.

Thanks!