update index to include new tutorials

Author: j-atkins

docs/user-guide/tutorials/index.md

@@ -10,4 +10,6 @@ ADCP_data_tutorial.ipynb
 CTD_data_tutorial.ipynb
 Drifter_data_tutorial.ipynb
 Argo_data_tutorial.ipynb
+CTD_transects.ipynb
+ADCP_transects.ipynb
 ```