Update summary with volume mode conversion doc

Author: RaunakShah

book/src/SUMMARY.md

@@ -40,6 +40,7 @@
  - [Token Requests](token-requests.md)
  - [FSGroup Support](support-fsgroup.md)
  - [CSI Windows](csi-windows.md)
+ - [Volume Mode Conversion](prevent-volume-mode-conversion.md)
 - [Deploying a CSI Driver on Kubernetes](deploying.md)
  - [Example](example.md)
 - [Driver Testing](testing-drivers.md)