Add an option to traverse the mutation result inclusively

[BelfordZ]

The test would look something like:

  it("it has an option for traversing the mutation results inclusively", () => {
    const testSchema = {
      type: "object"
    };
    const mergeProducer = jest.fn((s: CoreSchemaMetaSchema) => ({
      ...s,
      properties: {
        foo: { type: "string" }
      }
    }));

    const opts = { traverseMutationResult: true };

    const result = traverse(testSchema, mergeProducer, opts) as CoreSchemaMetaSchema;

    expect(result.properties).toBeDefined();

    expect(mergeProducer).toHaveBeenCalledTimes(2);
  });