[其它]webpack bug: configuration.module.rules[0].test: The provided value ".css$" is not an absolute path

在使用webpack中，配置loader解析器时，代码如下：

module:{
        rules:[{
            test:"\.css$",
            use:['style-loader','css-loader']
        }]
    }

报错：

× ｢wds｣: Invalid configuration object. Webpack has been initialised using a configuration object that does not match the API schema
.
- configuration.module.rules[0].test: The provided value ".css$" is not an absolute path!
pageage.json文件，对应版本信息如下：

"devDependencies": {
    "clean-webpack-plugin": "^3.0.0",
    "css-loader": "^3.1.0",
    "html-webpack-plugin": "^3.2.0",
    "style-loader": "^0.23.1",
    "webpack": "^4.36.1",
    "webpack-cli": "^3.3.6",
    "webpack-dev-server": "^3.7.2"
  }

然后，尝试把test 改成 /\.css$/ , 不使用双引号就好了（ps: 测试了一下，单引号也是不行的）。
代码如下：

module:{
        rules:[{
            test:/\.css$/,
            use:['style-loader','css-loader']
        }]
    }