feat(docs): add agent listing functions to IAssetManager documentation (#856)

Author: fassko

docs/fassets/reference/IAssetManager.mdx

@@ -86,6 +86,48 @@ function fAsset()
     returns (IERC20);
 ```
 
+## Agents
+
+### `getAvailableAgentsList`
+
+Returns the list of available agents.
+
+Parameters:
+
+- `_start`: First index to return from the available agent's list
+- `_end`: End index (one above last) to return from the available agent's list
+
+Returns:
+
+- `_agents`: The list of available agents
+- `_totalLength`: The total length of the available agents list
+
+```solidity
+function getAvailableAgentsList(uint256 _start, uint256 _end)
+    external view
+    returns (address[] memory _agents, uint256 _totalLength);
+```
+
+### `getAvailableAgentsDetailedList`
+
+Returns the list of available agents with extra information about agents like fee, minimum collateral ratio and available collateral (in lots).
+
+Parameters:
+
+- `_start`: First index to return from the available agent's list
+- `_end`: End index (one above last) to return from the available agent's list
+
+Returns:
+
+- `_agents`: The list of available agents with extra information
+- `_totalLength`: The total length of the available agents list
+
+```solidity
+function getAvailableAgentsDetailedList(uint256 _start, uint256 _end)
+    external view
+    returns (AvailableAgentInfo.Data[] memory _agents, uint256 _totalLength);
+```
+
 ## Redemption Queue
 
 ### `redemptionQueue`