NODEJS-680: Update and Automate TypeScript Support - 1. config and auth

[SiyaoIsTraveling]

I created tsconfig.json so that If you run tsc command, it will generate type declaration files .d.ts and source map files .d.ts.map in the folder dist/lib/. Therefore, our package.json needs to point main to lib/index.js and types to dist/lib/index.d.ts.

I also transformed the files in auth folder to clear most of the typescript errors. It mostly involves refactoring es5 classes to es6 classes.

I tested this config with GitHub private npm registry. I published the package privately and tested with a typescript client project. I confirm the type hints and IDE support is working fine for me.

To consider in the future:

1. License headers?
2. Bundling?

[SiyaoIsHiding]

Closing because we want to migrate to TypeScript entirely: #435