fix(npm): downgrade typescript to 3.6.5 for Angular v8 compatibility

Fixes #1168

Author: ocombe

package-lock.json

@@ -45,7 +45,7 @@
     "tsickle": "^0.35.0",
     "tslib": "^1.10.0",
     "tslint": "^5.20.1",
-    "typescript": "3.7.5"
+    "typescript": "3.6.5"
   },
   "config": {
     "commitizen": {