I have a problem with the Laravel 8 framework. I tried to install NPM to work under the concept of Laravel Mix. My problem is that the CSS and JS do not compile.

webpack.mix.js

mix.js('resources/js/app.js', 'public/js')
    .postCss('resources/css/app.css', 'public/css', [ 
        //
]) ;

package.json

 {
    "private": true,
    "scripts": {
        "dev": "npm run development",
        "development": "mix",
        "watch": "mix watch",
        "watch-poll": "mix watch -- --watch-options-poll=1000",
        "hot": "mix watch --hot",
        "prod": "npm run production",
        "production": "mix --production"
    },
    "devDependencies": {
        "@popperjs/core": "^2.10.2",
        "axios": "^0.21",
        "bootstrap": "^5.1.3",
        "laravel-mix": "^6.0.6",
        "lodash": "^4.17.19",
        "postcss": "^8.1.14",
        "resolve-url-loader": "^3.1.4",
        "sass": "^1.43.4",
        "sass-loader": "^11.1.1"
    }
}