docs(aio): add hero “Zero” to toh-6

Update to in-memory-web-api should handle id=0.
Make sure this works by having a hero with id=0 in ToH.
Coincidentally delete lingering dead app/ folders
Todo: fix ToH images (which have to do anyway)

aio/content/examples/toh-pt4/src/app/mock-heroes.ts

@@ -2,14 +2,14 @@
 import { Hero } from './hero';
 
 export const HEROES: Hero[] = [
-  {id: 11, name: 'Mr. Nice'},
-  {id: 12, name: 'Narco'},
-  {id: 13, name: 'Bombasto'},
-  {id: 14, name: 'Celeritas'},
-  {id: 15, name: 'Magneta'},
-  {id: 16, name: 'RubberMan'},
-  {id: 17, name: 'Dynama'},
-  {id: 18, name: 'Dr IQ'},
-  {id: 19, name: 'Magma'},
-  {id: 20, name: 'Tornado'}
+  { id: 11, name: 'Mr. Nice' },
+  { id: 12, name: 'Narco' },
+  { id: 13, name: 'Bombasto' },
+  { id: 14, name: 'Celeritas' },
+  { id: 15, name: 'Magneta' },
+  { id: 16, name: 'RubberMan' },
+  { id: 17, name: 'Dynama' },
+  { id: 18, name: 'Dr IQ' },
+  { id: 19, name: 'Magma' },
+  { id: 20, name: 'Tornado' }
 ];