Add example queries to the website

[wtrocki]

Add example minimal schema and queries that will be possible for that particular schema.

[ralfhandl]

RSDL schema missing.

Queries should be covered in https://rapid.rocks/docs/rapid-read

[mikepizzo]

We need to add RSDL schema prior to rapid-read walkthrough in order to provide the context of the schema.

The schema is present (at least in parts) in the RSDL Schema doc.