CIP-0116 | Add Conway JSON schema (#912)

* WIP: conway JSON spec

* Add TransactionWitnessSet

* Add GovAction type

* Require Withdrawals to be non-empty

* Add TransactionMetadatum

* WIP: conway json-schema

* Fix: minLength -> minItems

* WIP: add Vote, Voter & more

* Add missing types

* WIP: certs

* Remove `minItems` from withdrawals

* Remove duplicate TransactionMetadatum entry

* Specify the era in the schema titles

* Minor fixes to schemas

* Change additionalProperties to unevaluatedProperties to allow for inheritance

* Add required properties to NonnegativeInterval

* Add examples for some types

* fixing indentation white space to ensure done before merge

Co-authored-by: Ryan <[email protected]>

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Co-authored-by: Giovanni Garufi <[email protected]>
Co-authored-by: Giovanni Garufi <[email protected]>
Co-authored-by: Robert Phair <[email protected]>
Co-authored-by: Ryan <[email protected]>