Resolve examples for shared schemas

[vascofg]

The examples keyword is never transformed to example for shared schemas (added via fastify.addSchema and referred with $ref).

This PR calls the appropriate function on preparation of these shared schemas.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[mcollina]

lgtm

[vascofg]

Any chance you can release a new version anytime soon, including these changes?