Publish JSON schemas for context types to FDC3 website

[rikoe]

To finalise the JSON schema work for context schemas began with #120, a number of things need to be done:

• Identify which schemas should be officially published/standardised as part of the first pass. Cross-reference with Financial Objects. fdc3.instrument and fdc3.contact are the most important ones to start with.
• Remove everything apart from email property from fdc3.contact schema to simplify.
• Publish versioned schema definition files to the FDC3 website, to match the URLs in the schema files, e.g. https://fdc3.finos.org/schemas/1.0/instrument.schema
• Make sure the context data examples line up with the schema definitions
• Add documentation for each signed of schema to the context data website documentation. It could work similarly to e.g. the API reference documentation.

[lspiro-Tick42]

NB I think InstrumentSchema has moved to https://github.com/finos/FDC3/blob/master/src/context/schemas/instrument.schema