Make some functionality available for client side usage.

[earlAchromatic]

I can imagine scenarios where I have a big NotionCMS object generated and passed to the client for further on-the-fly manipulation to generate some UI items dynamically. Maybe you want to filter a list by tags or something.

The logic for doing so exists in the NotionCMS class but is currently unavailable for client side usage. We don't necessarily need to support any Notion communication, just data manipulation. We should consider a NotionCMS data object class that is both used by NotionCMS internals and exported for client usage to fill this need.