fix: `unplugin-typegpu` exports .ts file when imported from `workspace:*`

[cieplypolar]

We cannot test if unplugin-typegpu works correctly when used in babel.config.js.
The reason is that we locally export only .ts file.

Expected:

module.exports = (api) => {
  api.cache(true);
  return {
    presets: ['next/babel'],
    plugins: ['unplugin-typegpu/babel'], // cannot parse .ts file
  };
};

Current:

module.exports = (api) => {
  api.cache(true);
  return {
    presets: ['next/babel'],
    plugins: ['./node_modules/unplugin-typegpu/dist/babel.js'],
  };
};

[iwoplaza]

We could use the same mechanism we use for the typegpu package, and expose the built package artifacts under unplugin-typegpu/babel/$built$