fixing tabbing

CONTRIBUTING.md

@@ -111,7 +111,7 @@ The Fasten source code is organized into a handful of important folders, which w
 
 ## Frontend
 
-```tree
+```
 ├── frontend
 │   ├── src
 │   │   ├── app
@@ -171,7 +171,7 @@ The Fasten source code is organized into a handful of important folders, which w
 The backend is incredibly simple (by design). The hope is to remove it completely if possible, allowing Fasten to be served by 
 a CDN or minimal Nginx deployment. 
 
-```
+```tree
 ├── backend
 │   ├── cmd
 │   └── pkg
@@ -189,7 +189,7 @@ a CDN or minimal Nginx deployment.
 
 ## Distribution/Docker
 
-```
+```tree
 ├── docker-compose.yml                  # docker-compose file which can be used to compile and run "all-in-one" image
 ├── Dockerfile                          # dockerfile for "all-in-one" image, containing frontend, backend & database
 ├── docker