Add custom how-to guides to documentation, additional notebook around how to use dev cli

docs/source/how_to_guides/custom_rewards.rst

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+.. only:: comment
+
+    © Crown-owned copyright 2025, Defence Science and Technology Laboratory UK
+
+.. _custom_rewards:
+
+Creating Custom Rewards in PrimAITE
+***********************************
+
+Rewards within PrimAITE are contained within ``rewards.py``, which details the rewards available for all agents within training sessions, how they are calculated and any other specific information where necessary.
+
+Custom Rewards within PrimAITE should inherit from the ``AbstractReward`` class, found in ``rewards.py``. It's important to include an identifier for any class created within PrimAITE.
+
+.. code:: Python
+
+    class ExampleAward(AbstractReward, identifier="ExampleAward"):
+        """Example Reward Class """
+
+        def calculate(self, state: Dict, last_action_response: "AgentHistoryItem") -> float:
+            """Calculate the reward for the current state."""
+            return 1.0
+
+        @classmethod
+        def from_config(cls, config: dict) -> "AbstractReward":
+            """Create a reward function component from a config dictionary."""
+            return cls()
+
+
+Custom rewards that have been created should be added to the ``rew_class_identifiers`` dictionary within the ``RewardFunction`` class in ``rewards.py``.
+
+Including Custom Rewards within PrimAITE configuration
+======================================================
+
+Custom rewards can then be included within an agents configuration by it's inclusion within the training session configuration YAML.
+
+.. code:: yaml
+
+    agents:
+      - ref: agent_name
+        reward_function:
+          reward_components:
+            - type: DUMMY
+              weight: 1.0
+
+
+More detailed information about rewards within PrimAITE can be found within :ref:`Rewards`