Support for other keywords

[duncandewhurst]

Open-Telecoms-Data/open-fibre-data-standard#274 makes use of the additionalProperties keyword, which is not currently rendered by the directive.

Rather than adding columns for each possible JSON Schema keyword, perhaps we could have something like a 'constraints' column:

Field	Description	Type	Required	Constraints
readyForServiceDate	Ready for service date: The date this span was ready to carry traffic. For spans with multiple network providers, the earliest of the dates at which each provider’s network was ready to carry traffic on this span.	string		format: date
route	Span route: In the JSON publication format, a GeoJSON LineString geometry describing the route of this span. In the CSV publication format, a well-known text LINESTRING geometry. See Geometry	object		additionalProperties: false

In the meantime, I've handled this by updating the script that generates the schema reference documentation to add some text above the schema table to indicate to readers that additional properties are not permitted.

A side note, but I think we should also be documenting the meaning of the keywords and values in a standard's schema as part of that standard's documentation. In which case, the directive could link to those documentation pages so readers can find out, for example, what the date format is.