docs: create documentation for inference module

docs/source/inference/active_learning.rst

+Active Learning
+---------------
+
+ActiveLearning Class
+^^^^^^^^^^^^^^^^^^^^
+
+The :class:`.ActiveLearning` class is imported by::
+    
+    from psimpy.inference.active_learning import ActiveLearning
+
+Methods
+*******
+.. autoclass:: psimpy.inference.active_learning.ActiveLearning
+    :members: initial_simulation, iterative_emulation, approx_ln_pxl
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docs/source/inference/bayes_inference.rst

+Bayes Inference
+---------------
 
+GridEstimation Class
+^^^^^^^^^^^^^^^^^^^^
+
+The :class:`.GridEstimation` class is imported by::
+    
+    from psimpy.inference.bayes_inference import GridEstimation
+
+Methods
+*******
+.. autoclass:: psimpy.inference.bayes_inference.GridEstimation
+    :members: run
+
+
+MetropolisHastingsEstimation Class
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+The :class:`.MetropolisHastingsEstimation` class is imported by::
+    
+    from psimpy.inference.bayes_inference import MetropolisHastingsEstimation
+
+Methods
+*******
+.. autoclass:: psimpy.inference.bayes_inference.MetropolisHastingsEstimation
+    :members: run

docs/source/inference/index.rst

+Inference
+=========
+
+This module hosts functionality for inference methods.
+
+Currently implemented classes are:
+
+* :class:`.ActiveLearning`:
+
+* :class:`.GridEstimation`:
+
+* :class:`.MetropolisHastingsEstimation`:
+
+.. toctree::
+   :maxdepth: 1
+   :hidden:
+   :caption: Inference
+
+    Active Learning <active_learning>
+    Bayes Inference <bayes_inference>
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