Use more explicit types in the json schema instead of just "string".

[jh-RLI]

Description of the issue

The JSON schema spec allows some build in additional types.

Ideas of solution

Since we are currently doing a rewrite of omi checking sting types against python types is not how we want to do this anymore. Using the tooling around json schema is a better solution.

We need to update the type field for each element in the json schema if the value can be described as something else than "string".

Workflow checklist

• I am aware of the workflow in CONTRIBUTING.md

[jh-RLI]

FYI
@henhuy @christian-rli