add versionadded tags

doc/src/Packages_details.rst

@@ -1407,6 +1407,8 @@ expressions, they are more precise than what can be done with
 **Authors:** Axel Kohlmeyer (Temple U).  Lepton itself is developed
 by Peter Eastman at Stanford University.
 
+.. versionadded:: TBD
+
 **Install:**
 
 This package has :ref:`specific installation instructions <lepton>` on

doc/src/bond_lepton.rst

@@ -28,6 +28,8 @@ Examples
 Description
 """""""""""
 
+.. versionadded:: TBD
+
 Bond style *lepton* computes bonded interactions between two atom
 based on evaluating strings.  The potential function must be provided as an
 expression string using "r" as the distance variable relative to the

doc/src/pair_lepton.rst

@@ -34,6 +34,8 @@ Examples
 Description
 """""""""""
 
+.. versionadded:: TBD
+
 Pair style *lepton* computes spherical pairwise interactions based on
 evaluating strings.  The potential function must be provided as an
 expression string using "r" as the distance variable, for example