add css & style loader

package.json

@@ -19,7 +19,9 @@
   },
   "homepage": "https://github.com/zhandouxiaojiji/behavior3editor#readme",
   "devDependencies": {
+    "css-loader": "^4.3.0",
     "source-map-loader": "^1.1.0",
+    "style-loader": "^2.0.0",
     "ts-loader": "^8.0.4",
     "typescript": "^4.0.3",
     "webpack": "^4.44.2",