Module-arization / STAC and Clean-up

[jo-chemla]

• Important Feature: Proxy server middleware when app will not be client only, to remove the need for Allow-CORS plugin. Would be great to be a complete STAC catalog endpoint - translating each aggregator API into a fully compliant STAC API.

• Put API search in its own typescript module

• eventually yield results the way loaders.gl does it, via a stream, especially for multi-page or multi-providers searches on each api

• Cleanup: search-utilities, make each search extends a search object class, polygon aoi be a single feature search param, each geojson feature be a real geojson feature (search input, results)