Add json-transforms module

[cursor]

Add a new Maven submodule json-transforms implementing the Microsoft json-document-transforms specification.

Goals:

• Provide a Java 21+ implementation using jdk.sandbox.java.util.json values.
• Parse/compile phase that precompiles JSONPath selectors for reuse.
• Run phase that applies transforms immutably.
• Port the reference C# test suite inputs/expected cases.
• Document the module in top-level README and in json-transforms/README.md.

Spec reference: https://github.com/Microsoft/json-document-transforms/wiki
Reference implementation: https://github.com/microsoft/json-document-transforms