fix: package json export for publish

[wseymour15]

Description

When attempting to publish the package, npm publish was giving me the following error:

Error in dist/videojs-overlay.cjs.js:
node:internal/modules/cjs/loader:641
      throw e;
      ^

Error [ERR_PACKAGE_PATH_NOT_EXPORTED]: No "exports" main defined in /private/var/folders/5f/.../node_modules/videojs-overlay/package.json

This change fixes the issue, and has been tested with dry-run

Specific Changes proposed

• Add default exports to package.json

Requirements Checklist

• Feature implemented / Bug fixed
• If necessary, more likely in a feature request than a bug fix
  • Unit Tests updated or fixed
  • Docs/guides updated
• Reviewed by Two Core Contributors