docs(ecosystem): add fn sphere and zod-compare

[lawvs]

• Introduce zod-compare to the Zod ecosystem list. zod-compare is a Zod Utilities package that recursively compares zod schemas.
• Introduce Fn Sphere to the Zod ecosystem list; it delivers a Zod-first toolkit for building powerful, type-safe filter experiences across web apps.

Using Zod as a runtime DSL is an intriguing approach, and I am convinced that there will be more practical applications in the future.