Merge pull request 'fixed typo in tree' (!153) from dev_docs into development

Reviewed-on: #153

docs/hero_create_mdbook.md

@@ -57,8 +57,8 @@ We first show the directory tree template to give an overview of the project. Wi
     └── new_mdbook
         ├── book_collections.md
         ├── context.md
-│       ├── SUMMARY.md
-│       └── sync_production.sh
+        ├── SUMMARY.md
+        └── sync_production.sh
 ```
 
 ### Files and Directories Example