feat(@schematics/angular): use isolatedModules in generated project

As 3acb776 introduced an optimization for projects that use `isolatedModules`,
this commit makes projects generated with `ng new` use this option by default.

Author: cexbrayat

packages/schematics/angular/workspace/files/tsconfig.json.template

@@ -10,6 +10,7 @@
     "noImplicitReturns": true,
     "noFallthroughCasesInSwitch": true,<% } %>
     "skipLibCheck": true,
+    "isolatedModules": true,
     "esModuleInterop": true,
     "sourceMap": true,
     "declaration": false,