Add MockServer expectations JSON Schema

[jamesdbloom]

Summary

Adds the MockServer expectations JSON Schema to the catalog as an external/self-hosted schema.

• Schema URL: https://www.mock-server.com/schema/expectations.json
• Type: Self-hosted (external)
• Draft: draft-07

File match patterns

Pattern	Description
mockserverInitialization.json	Default MockServer initialization file
*mockserver*Initialization.json	Custom initialization files containing "mockserver" and "Initialization"
mockserver*.json	Any JSON file starting with "mockserver"

Context

MockServer is an open-source HTTP(S) mock server and proxy for testing (GitHub). Users configure expectations as JSON arrays. The schema enables IDE autocompletion and validation for these files.

This was requested in mock-server/mockserver#1883.

The schema is self-contained (all $ref definitions inlined) and validates correctly with jsonschema and ajv.

[github-actions]

Thanks for the PR!

This section of the codebase is owned by @madskristensen and @hyperupcall - if they write a comment saying "LGTM" then it will be merged.