Enable neighbor tools in api docs. (#1086)

Author: coreyjadams

docs/api/physicsnemo.utils.rst

@@ -22,6 +22,16 @@ These are particularly useful when implementing custom training loops or special
     :members:
     :show-inheritance:
 
+Neighbor utils
+--------------
+
+Utilities for optimized layers for neighbor searches.
+
+.. automodule:: physicsnemo.utils.neighbors
+    :members:
+    :show-inheritance:
+
+
 GraphCast utils
 ---------------
 

physicsnemo/utils/neighbors/__init__.py

@@ -16,3 +16,6 @@
 
 
 from .radius_search import radius_search
+
+# This is exclusively for the autodoc to generate the api docs:
+__all__ = ["radius_search"]