Update README with a description of this project

[cjcenizal]

When folks visit a project, they need a README that can help them understand the project's value to them and how they can try it out. See https://github.com/vectara/vectara-ingest for an example of a README structure that I think will help us with this.

I propose we:

• Apply the same README structure from Vectara Ingest, especially the About, Quickstart, Author, Contributing, and License sections.
• Create a CONTRIBUTING.md file to encapsulate maintenance information.