create-react-app 添加less支援

首先修改/node_modules/react-scripts/config/目錄下的webpack.config.prod.js和webpack.config.dev.js，将對應的css子產品添加less loader：

// "postcss" loader applies autoprefixer to our CSS.
          // "css" loader resolves paths in CSS and adds assets as dependencies.
          // "style" loader turns CSS into JS modules that inject <style> tags.
          // In production, we use a plugin to extract that CSS to a file, but
          // in development "style" loader enables hot editing of CSS.
          {
            test: /\.(css|less)$/,
            use: [
              require.resolve('style-loader'),
              {
                loader: require.resolve('css-loader'),
                options: {
                  importLoaders: 1,
                },
              },
              {
                loader: require.resolve('postcss-loader'),
                options: {
                  // Necessary for external CSS imports to work
                  // https://github.com/facebookincubator/create-react-app/issues/2677
                  ident: 'postcss',
                  plugins: () => [
                    require('postcss-flexbugs-fixes'),
                    autoprefixer({
                      browsers: [
                        '>1%',
                        'last 4 versions',
                        'Firefox ESR',
                        'not ie < 9', // React doesn't support IE8 anyway
                      ],
                      flexbox: 'no-2009',
                    }),
                  ],
                },
              },
			  {
				  loader: require.resolve('less-loader'),
			  }
            ],
          },
           

修改兩個檔案的這兩處，儲存之後在項目中通過npm或者yarn添加less和less-loader就可以在項目中使用