Create JSON schema for the OpenIndexMaps 1.0.0 Specification

[srappel]

Creating a JSON schema for OpenIndexMaps would help GeoBlacklight development efforts to integrate OpenIndexMaps.

Most of the support for OIM in GeoBlacklight was developed for the 0.0.0 Specification.

[srappel]

Putting this here for future reference:
https://json-schema.org/learn/getting-started-step-by-step

[srappel]

One thing we're finding out is that if you enter a element incorrectly (e.g. thumbURL instead of the correct thumbUrl), the GeoJSON will still validate because it will assume that the incorrect element is just a local element not defined in the spec.

Perhaps we could consider making this spec specifically fail if it's missing elements required for inclusion in GeoBlacklight?