publish libs package

[PacoDu]

Hi, it would be really nice to have a package that exposes the library index https://github.com/stac-utils/stac-server/blob/master/libs/index.js so anyone can use the API implementation and deploy it as needed.

For exemple we easily plugged the library to fastify (because we don't use AWS cloud or have access to a FaaS). But currently we have to fork the repo in order to achieve this. Publishing the libs/index.js package would easily split the web server implementation/deployment from the main library. And maybe in a near future we could imagine some plugin packages like stac-server-(express|fastify|hapi|serverless) that can leverage the base library independently of the web server implementation used.

Anyway thanks for this work, it gave us a great idea of what we can achieve with the stac spec !