Add @ontologies/core

[joepio]

More info on the project: https://ontola.io/blog/ontologies-in-js/

To improve the usability of RDFJS tools,
we recommend all listed libraries to have the following elements in their documentation (README or linked).
Please select all elements that apply for your library:

• General description: High-level description of tool and available features.
• Installation: How to install and import into project.
• Usage: Describing the main features with code examples.
• Configuration: The available config options for this tool, e.g. constructor params.
• Specification Compliance: Mention the compliance with respect to any (W3C) specification, including RDFJS interfaces.
• License: The license under which the library is available.

[ktk]

@joepio could we align that somehow with https://github.com/zazuko/rdf-vocabularies/?