Finalize library

[ekrengel]

We need to do something to get this ready for release.

• [x] (Justin) Improve usability of creating new AWSGuard policy pack instance and configuring individual policies.
• [x] (Justin) Readme
• [x] (Justin) Documentation on how to use this library. Maybe a step by step guide on creating a new policy pack and importing/configuring these rules. (PR https://github.com/pulumi/docs/pull/2056)
• [x] (Justin) Add to docs site where appropriate (PR https://github.com/pulumi/docs/pull/2056)
• [x] (Chris) Add license (and any other missing fields) to package.json
• [x] (Chris) Publish to npm, so it can be used as configurable library
• [x] (Justin) Consider adding a policy template to make it easy to get started using AWSGuard.