Add support for additional types to @kbn/config-schema

[joshdover]

This is an open issue used to track additional types that may need to be added to the @kbn/config-schema package to support validation.

Note that the Platform Team is working on decoupling HTTP validation from this library while maintaining compatibility (#50179). We do not yet have a long-term solution or plan for HTTP validation and may not use this package for that usecase.

In light of that, we may choose not to add all types needed for HTTP validation to this config schema library.

Types to add (edit this issue to add more):

• Date

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)