Invalid refs in json schema

[robertdanci]

Some of the refs in the JSON schema cannot be resolved, more specifically the following:

• https://github.com/internetarchive/openlibrary-client/blob/master/olclient/schemata/work.schema.json#L29
• https://github.com/internetarchive/openlibrary-client/blob/master/olclient/schemata/shared_definitions.json#L10

[robertdanci]

See PR with fix: #431