chore(ngxs-demo): fix "Person State" demo (#1528)

Author: hakimio

apps/ngxs-demo/json/person.json apps/ngxs-demo/assets/person.jsonapps/ngxs-demo/json/person.json renamed to apps/ngxs-demo/assets/person.json

@@ -11,7 +11,7 @@ export class PersonService {
 
     public fetchAll(): Observable<PersonModel> {
         return this.httpService
-            .get<{data: PersonModel}>('./app/json/person.json')
+            .get<{data: PersonModel}>('./assets/person.json')
             .pipe(map((response: {data: PersonModel}): PersonModel => response.data));
     }
 }