Simplify README a bit to more strongly recommend a default usage

[RickMoynihan]

Some improvements to the README.

Mainly just orientating it around using deps.edn as the prefered way of building and including validation suites, and moving finer details of other approaches that people wanting to get started don't need to know immediately into supporting documents in the docs folder.

[jennet]

This is really nicely written 👍 @RickMoynihan

At this point

You'll then want to configure some validation suites and supply it with the location of some RDF (either via a SPARQL endpoint) or as a file of triples.

It might be useful to have an example of simply running the rdf-validator against an endpoint with a single sparql query file (i.e. expand slightly on the $ clojure -A:rdf-validator <ARGS>) before jumping in to defining/including suites.

[RickMoynihan]

Agreed that would be useful, though better yet I think would be for our example validations to be designed to run against a public site, e.g. scotland's SPARQL endpoint.

The example validation suite could include a single passing and a single failing validation for example e.g.

• ✅ Every dataset on scotland has a label
• ⚠️ Every qb:Dataset defines a :gender dimension (or some other validation that should purposefully always fail).

That way users could run the example immediately, then tweak to their data/endpoint.

[RickMoynihan]

We could maybe do this as another PR?

[jennet]

Added issue for the examples enhancement to the README #30

[jennet]

Happy to go with this restructuring and rewrite