Publish browser compatible

[EdwinOtten]

Update the project to use rollup.js for building a browser-compatible library.

• Add rollup configuration:

  • Add rollup.config.js to configure rollup.js for building the library.
  • Include input as src/index.ts and output as dist/sportlink-to-mailchimp-converter.umd.js.
  • Use plugins for TypeScript and node resolution.

• Update package.json:

  • Update the build script to use rollup.js.
  • Add rollup.js and related plugins as dependencies.
  • Change the main and types fields to point to the rollup output.
  • Set the type field to module.

• Update package-lock.json:

  • Add rollup.js and related plugins as dependencies.
  • Downgrade jest and related dependencies to version 29.1.1.

• Update tsconfig.json:

  • Ensure compatibility with rollup.js and browser environments.
  • Add a types field to include @jest/globals.
  • Exclude files with names ending with "test.ts".

• Update README.md:

  • Include instructions for using the library in browser script tags and client-side applications.