Add SO(3)/O(3)-averaging calculator wrappers (#85)

Author: ppegolo

docs/src/engines/ase.rst

@@ -23,6 +23,10 @@ Supported model outputs
   :py:meth:`ase.Atoms.get_forces`, …);
 - arbitrary outputs can be computed for any :py:class:`ase.Atoms` using
   :py:meth:`MetatomicCalculator.run_model`;
+- for non-equivariant architectures like
+  `PET <https://docs.metatensor.org/metatrain/latest/architectures/pet.html>`_,
+  rotationally-averaged energies, forces, and stresses can be computed using
+  :py:class:`metatomic.torch.ase_calculator.SymmetrizedCalculator`.
 
 How to install the code
 ^^^^^^^^^^^^^^^^^^^^^^^

docs/src/torch/reference/ase.rst

@@ -17,3 +17,7 @@ not just the energy, through the
 .. autoclass:: metatomic.torch.ase_calculator.MetatomicCalculator
     :show-inheritance:
     :members:
+
+.. autoclass:: metatomic.torch.ase_calculator.SymmetrizedCalculator
+    :show-inheritance:
+    :members: