Expose stylesheet from an NPM package ([ref](https://github.com/vitejs/vite/discussions/2657#discussioncomment-1345262))

package.json

{
  // ...
  "exports": {
    ".": {
      "import": "./dist/main.mjs",
      "require": "./dist/main.cjs"
    },
    "./style.css": {
      "import": "./dist/style.css",
      "require": "./dist/style.css"
    }
  }
  // ...
}