Add multivariate Gaussian model to runner in docs

Author: Toni-SM

skrl/utils/runner/torch/runner.py

@@ -14,7 +14,13 @@
 from skrl.resources.schedulers.torch import KLAdaptiveLR  # noqa
 from skrl.trainers.torch import SequentialTrainer, Trainer
 from skrl.utils import set_seed
-from skrl.utils.model_instantiators.torch import categorical_model, deterministic_model, gaussian_model, shared_model
+from skrl.utils.model_instantiators.torch import (
+    categorical_model,
+    deterministic_model,
+    gaussian_model,
+    multivariate_gaussian_model,
+    shared_model,
+)
 
 
 class Runner:
@@ -37,6 +43,7 @@ def __init__(self, env: Union[Wrapper, MultiAgentEnvWrapper], cfg: Mapping[str,
             "gaussianmixin": gaussian_model,
             "categoricalmixin": categorical_model,
             "deterministicmixin": deterministic_model,
+            "multivariategaussianmixin": multivariate_gaussian_model,
             "shared": shared_model,
             # memory
             "randommemory": RandomMemory,