feat/types: add main and types fields

[cncolder]

• generate type difinition files
• tsdx is requireable now
  • so user can put TsdxOptions into tsdx.config.js JSDoc

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[cncolder]

I copy TsdxOptions into externalTypes.ts. So user cannot explore more types in editor. e.g. Cmd+Click in vscode.

Update comments to JSDoc. So comments will emit into externalTypes.d.ts

I'm not sure if we need exclude another .d.ts files from npm. I wish leave there. It's cool if someone find code suggestions when require('tsdx/dist/createJestConfig')

[cncolder]

So now. What's your favor @agilgur5 ?

1. Active "declaration" in tsconfig.json. Then re-export TsdxOptions from types.ts.
2. Disable "declaration". And add a new file to npm like types/index.d.ts. But we still need main field in package.json