docs: Document valid size range for network volumes (#598)

Author: muhsinking

flash/configuration/storage.mdx

@@ -65,6 +65,8 @@ async def process(data: dict) -> dict:
     ...
 ```
 
+The `size` parameter specifies the volume size in GB. Valid values range from 10 to 4096 GB (4 TB). If not specified, `size` defaults to 100 GB.
+
 You can also reference an existing volume by ID:
 
 ```python