add isolatedModules: true to app

Author: dynst

apps/rxjs.dev/tsconfig.json

@@ -6,6 +6,7 @@
     "outDir": "./out-tsc",
     "forceConsistentCasingInFileNames": true,
     "strict": true,
+    "isolatedModules": true,
     "noImplicitOverride": true,
     // NOTE: Intentionally deviate from default Angular CLI settings
     //       (due to many violations and uglier syntax).
@@ -45,4 +46,4 @@
     "strictInputAccessModifiers": true,
     "strictTemplates": true
   }
-}
+}