update[documentation]: add y branch autograd level set to the documentation

Author: Gregory Roberts

docs/features/autograd.rst

@@ -18,6 +18,7 @@ The adjoint method is an extremely powerful tool for photonics optimization, all
     ../../Autograd7Metalens
     ../../Autograd8WaveguideBend
     ../../Autograd9WDM
+    ../../Autograd10YBranchLevelSet
     ../../Autograd13Metasurface
     ../../Autograd12LightExtractor
     ../../Autograd15Antenna