optimize publish related settings

[LoTwT]

Situation

In #9, it fixes the playground import in a hacked way which adds the ./dist field of the exports in the package.json.

Alternative solution

I think adding a files field in the package.json is a better solution.

• remove the ./dist of the publish() in the .build.mjs
• add files in the package.json

  {
    "files": ["dist"]
  }

• update related fields in the package.json such as exports, main, module, and types
• pnpm build and can also run npm pack --dry-run to see the tarball contents if need
• change the import statements in the playground

After doing the above, I think the imports and exports are unified.