Update dependency typescript to v4

Author: renovate-bot

package.json

@@ -49,7 +49,7 @@
     "mocha": "^7.0.1",
     "npm-run-all": "^4.1.5",
     "nyc": "^15.0.0",
-    "typescript": "^3.5.3"
+    "typescript": "^4.4.4"
   },
   "dependencies": {
     "strftime": "^0.10.0",