Improve css prebuilt creation and minimize (#5553)

* improve CSS creation strategy and minimize

* remove multiple select slow down test

package.json

@@ -147,9 +147,9 @@
     "commander": "4.0.0",
     "concurrently": "^3.5.1",
     "cspell": "^3.1.3",
+    "css-loader": "^3.4.2",
     "dotenv": "6.2.0",
     "ejs": "^2.6.1",
-    "extract-text-webpack-plugin": "^4.0.0-beta.0",
     "fs-extra": "^4.0.2",
     "graphql": "^14.1.1",
     "husky": "^1.2.0",
@@ -178,10 +178,12 @@
     "mdast-util-heading-range": "^2.1.0",
     "mdast-util-toc": "^2.0.1",
     "mdast-zone": "^3.0.1",
+    "mini-css-extract-plugin": "^0.9.0",
     "nconf": "^0.10.0",
     "ncp": "^2.0.0",
     "ng-packagr": "4.7.1",
     "node-sass": "4.13.0",
+    "optimize-css-assets-webpack-plugin": "^5.0.3",
     "protractor": "^5.4.2",
     "protractor-browser-logs": "1.0.456",
     "protractor-html-reporter-2": "1.0.4",
@@ -209,8 +211,7 @@
     "unist-util-select": "^2.0.0",
     "url-join": "^4.0.0",
     "webpack-bundle-analyzer": "^3.3.2",
-    "webpack-cli": "^3.1.0",
-    "webpack-merge": "2.6.1"
+    "webpack-cli": "^3.1.0"
   },
   "license": "Apache-2.0",
   "bundlesize": [