[Ruby] Release 0.45.0

Added

• JSONSchema.bundle(schema, ...): produce a Compound Schema Document with all external $ref targets embedded in a draft-appropriate container (definitions for Draft 4/6/7, $defs for Draft 2019-09/2020-12; Appendix B). #791.
• ValidationError#absolute_keyword_location to get the absolute keyword location URI of the schema node that produced the error.