Update dependency typescript to v3.9.5 (#94)

Author: renovate-bot

package.json

@@ -54,7 +54,7 @@
     "rollup": "2.7.3",
     "tap": "14.10.7",
     "tslib": "1.11.1",
-    "typescript": "3.8.3",
+    "typescript": "3.9.5",
     "typescript-esm": "1.0.1"
   },
   "volta": {