Align project package.json with best practices

[djarekg]

Follow recommendations in Open WC - Publishing.

Missing properties to add to package.json

• "main": "./src/index.js"
• "module": "./src/index.js"
• exports
  • Add index.ts to /src direcotory
  • If adding index.ts to /src is not enough to expose public files, then also add an entry for each exported file.