[Server][Conformance] Support for resource with binary content missing #213

Not sure about this one, but to me it looks like the support for resources with binary content is missing, and therefore I could implement scenario resources-read-binary, see examples/server/conformance/server.php.

Reproduce:

make conformance-server

npx @modelcontextprotocol/conformance server --url http://localhost:8000 --scenario resources-read-binary