feat(dts-generator): add TypedJSONModel - trying, wip, do not submit

[akudev]

Add the type definitions for the TypedJSONModel and adapt the generator to insert them to the core d.ts file.

[codeworrior]

Isn't this approach totally lacking an entry in the API Reference in the SDK?

[akudev]

@codeworrior Yes, and intentionally so, as the API makes no sense for JS developers and would only confuse.
The discoverability for TS developers is of course limited, but isn't that the case for other TS-specific tweaks already, like in the area of ControllerExtensions?
I'd argue that the place for discovering features is either the fulltext documentation (where this should be added) or samples (dito) or the in-editor API suggestions. Not many read the API doc to find out which feature they might want to use.
But we can of course easily add JSDoc saying "only makes a difference in TS".