Add install for rollup

[dangvanthanh]

Add install for rollup in README.md

[super-fool]

@dangvanthanh when i use unplugin-vue2-script-setup/rollup, error is 'default' is not exported by ./Index.vue

export default {
  input: "./index.js",
  output: [
    {
      format: "es",
      file: "./dist/index.js",
      sourcemap: true,
    },
  ],
  plugins: [
    vue({
      css: false,
    }),
    scss(),
    css({ output: "index.css" }),
    nodeResolve(),
    scriptSetup({}),
    commonjs(),
    esbuild({
      minify: true,
    }),
  ],
};

[dangvanthanh]

@super-fool

You should move vue below scriptSetup. It's working

export default {
  input: "./index.js",
  output: [
    {
      format: "es",
      file: "./dist/index.js",
      sourcemap: true,
    },
  ],
  plugins: [
    scss(),
    css({ output: "index.css" }),
    nodeResolve(),
    commonjs(),
    scriptSetup({}),
    vue({
      css: false,
    }),
    esbuild({
      minify: true,
    }),
  ],
};