Add link to LittleFileSystem.md

Add storage config page to related content for consistent UX.

Author: Amanda Butler

docs/reference/api/storage/LittleFileSystem.md

@@ -42,3 +42,7 @@ The API that this presents is the standard Mbed OS file system API. Once declare
 ### LittleFileSystem example
 
 [![View code](https://www.mbed.com/embed/?url=https://github.com/armmbed/mbed-os-example-filesystem)](https://os.mbed.com/teams/mbed-os-examples/code/mbed-os-example-filesystem/file/8e251d9511b8/main.cpp)
+
+### Related content
+
+- [Storage configuration](configuration-storage.html).