chore: update gatsby to v3 (#5057)

website/content/docs/beta-features.md

@@ -634,7 +634,7 @@ collections:
 ```
 
 Nested collections expect the following directory structure:
-```
+```bash
 content
 └── pages
     ├── authors
@@ -646,4 +646,4 @@ content
         ├── hello-world
         │   └── index.md
         └── index.md
-```
+```