include instruction to server.validator(Joi);

[fabiomotta0311]

Context

• node version: 12.16.3
• module version: ^19

What are you trying to achieve or the steps to reproduce ?

In the Release#4017 was added the instruction to call server.validator in the server code but It still not included in the documentation page: https://hapi.dev/module/joi/

server.validator(Joi);

[fabiomotta0311]

Release#4017: hapijs/hapi#4017

[hueniverse]

Because that's a hapi api, not a joi api...