plugin: orama schema from json schema

[mrbrianevans]

Converts from json schema to orama schema format.

Sorry I didn't see that someone else had already opened a PR until after I'd implemented it.

Closes https://github.com/oramasearch/orama/issues/445.

Very simple implementation, doesn't resolve references. That can be done by many other packages on npm, this is just to convert from a fully resolved json schema.