support draft-07

[jba]

Some systems still use the old draft-07 version of the spec. This package should support it.

There is an existing PR elsewhere for this: modelcontextprotocol/go-sdk#220.

It contains a purported implementation, but that was AI-generated. It needs to be checked against the test suite for that draft.

[ghostsquad]

It seems many systems still use the draft-07 version. If you try to contribute to https://github.com/SchemaStore/schemastore and run their validation, they'll even warn you about this compatibility:

>> Found a too high schema version in file "./src/schemas/json/github-workflow.json"
>> Schema version "https://json-schema.org/draft/2020-12/schema" is not supported by many editors and IDEs
>> We recommend using a lower schema version.
>> To ignore this error, append to the "highSchemaVersion" key in "./src/schema-validation.jsonc"