Update dependency typescript to v3.9.3

Author: renovate-bot

package-lock.json

@@ -63,7 +63,7 @@
     "postcss-loader": "3.0.0",
     "sass-loader": "8.0.2",
     "ts-loader": "7.0.5",
-    "typescript": "3.8.3",
+    "typescript": "3.9.3",
     "webpack": "4.43.0",
     "webpack-cli": "3.3.6",
     "webpack-merge": "4.2.2",