Added the details on BatchedMetric or BatchedPerturbationMetric

CONTRIBUTING.md

@@ -142,6 +142,8 @@ The following methods are optimal for implementation:
 - `custom_preprocess()`: In case `general_preprocess()` from base class is not sufficient, additional preprocessing steps can be added here. This method must return a dictionary with string keys or None. If a dictionary is returned, additional keyword arguments can be used in `evaluate_instance()`. Please make sure to read the docstring of `custom_preprocess()` for further instructions on how to appropriately name the variables that are created in the function.
 - `custom_postprocess()`: Additional postprocessing steps can be added here that is added on top of the resuling evaluation scores.
 
+For computational efficiency gains, it might be wise to consider using the `BatchedMetric` or `BatchedPerturbationMetric` when implementing your new metric. Details on the specific implementation requirements can be found in the respective class method, please see: [quantus.readthedocs.io](https://quantus.readthedocs.io/en/latest/docs_api/quantus.metrics.html).
+
 ### Using Helpers
 
 In the `quantus/helpers` folder, you might find functions relevant to your implementation. Use search function and go through the function docstrings to explore your options.