Add support for authorization against external schema registries

[drpump]

User Story Description

As a Software Developer,

I want to supply credentials for HTTP retrievals of absolute$ref URLs,

so I can access an external schema/component registry that requires authentication

Acceptance Criteria

• Linter successfully downloads JSON schema from an absolute $ref URL that requires HTTP basic authentication
• Linter successfully downloads a JSON schema from an absolute $ref URL that requires HTTP token (Bearer) authentication

Sprint Ready Checklist

• Acceptance criteria defined
• Team understands acceptance criteria
• Team has defined solution / steps to satisfy acceptance criteria
• Acceptance criteria is verifiable / testable
• External / 3rd Party dependencies identified