feat: added tau ext to sim robot

Author: juelg

python/rcs/envs/sim.py

@@ -65,6 +65,7 @@ def step(self, action: dict[str, Any]) -> tuple[dict[str, Any], float, bool, boo
             info["collision"] = info["collision"] or state.collision
         info["ik_success"] = state.ik_success
         info["is_sim_converged"] = self.sim.is_converged()
+        obs["tau_ext"] = self.sim.data.qfrc_constraint[:7]
         # truncate episode if collision
         obs.update(self.unwrapped.get_obs())
         return obs, 0, False, info["collision"] or not state.ik_success, info