Add concurrently to dev dependencies

Author: kafiln

package.json

@@ -57,6 +57,7 @@
     "ts-jest": "^25.2.1",
     "ts-node": "^8.8.1",
     "tslint": "^6.1.0",
-    "typescript": "^3.8.3"
+    "typescript": "^3.8.3",
+    "concurrently": "^5.3.0"
   }
 }