Add some code comment

src/jaxsim/simulation/simulator.py

@@ -21,15 +21,19 @@
 @jax_dataclasses.pytree_dataclass
 class SimulatorData:
 
+    # Simulation time stored in ns in order to prevent floats approximation
     time_ns: jtp.Int = jnp.array(0, dtype=int)
 
+    # Terrain and contact parameters
     terrain: Terrain = jax_dataclasses.field(default_factory=lambda: FlatTerrain())
     contact_parameters: SoftContactsParams = jax_dataclasses.field(
         default_factory=lambda: SoftContactsParams()
     )
 
+    # Dictionary containing all handled models
     models: Dict[str, Model] = jax_dataclasses.field(default_factory=dict)
 
+    # Default gravity vector (could be overridden for individual models)
     gravity: jtp.Vector = jax_dataclasses.field(
         default_factory=lambda: jaxsim.physics.default_gravity()
     )
@@ -38,17 +42,23 @@ class SimulatorData:
 @jax_dataclasses.pytree_dataclass
 class JaxSim(JaxsimDataclass):
 
+    # Step size stored in ns in order to prevent floats approximation
     step_size_ns: jtp.Int = jax_dataclasses.field(
         default_factory=lambda: jnp.array(0.001, dtype=int)
     )
+
+    # Number of substeps performed at each integration step
     steps_per_run: jtp.Int = jax_dataclasses.static_field(default=1)
 
+    # Default velocity representation (could be overridden for individual models)
     velocity_representation: VelRepr = jax_dataclasses.field(default=VelRepr.Mixed)
 
+    # Integrator type
     integrator_type: ode_integration.IntegratorType = jax_dataclasses.static_field(
         default=ode_integration.IntegratorType.EulerForward
     )
 
+    # Simulator data
     data: SimulatorData = dataclasses.field(default_factory=lambda: SimulatorData())
 
     @staticmethod