@angular/cli migration - update-tsconfig-target

Update TypeScript compilation target to 'ES2020'.

Author: robertIsaac

tsconfig.json

@@ -14,7 +14,7 @@
     "experimentalDecorators": true,
     "moduleResolution": "node",
     "importHelpers": true,
-    "target": "es2015",
+    "target": "es2020",
     "module": "es2020",
     "lib": [
       "es2018",