chore: add HITL docs

Author: radu-mocanu

docs/human_in_the_loop.md

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+# Human In The Loop
+
+Guide for **Human-In-The-Loop** scenarios within the UiPath-LLamaIndex integration.
+It focuses on the **ctx.write_event_to_stream** LlamaIndex functionality.
+
+## Models Overview
+
+### 1. CreateAction
+
+The `CreateAction` model is utilized to create an escalation action within the UiPath Action Center as part of an interrupt context. The action will rely on a previously created UiPath app.
+After addressing the escalation, the current agent will resume execution.
+For more information on UiPath apps, refer to the [UiPath Apps User Guide](https://docs.uipath.com/apps/automation-cloud/latest/user-guide/introduction).
+
+#### Attributes:
+
+-   **name** (Optional[str]): The name of the app.
+-   **key** (Optional[str]): The key of the app.
+-   **title** (str): The title of the action to create.
+-   **data** (Optional[Dict[str, Any]]): Values that the action will be populated with.
+-   **app_version** (Optional[int]): The version of the app (defaults to 1).
+-   **assignee** (Optional[str]): The username or email of the person assigned to handle the escalation.
+
+#### Example:
+
+```python
+from uipath_llamaindex.models import CreateActionEvent
+action_output = ctx.write_event_to_stream(CreateActionEvent(name="AppName", title="Escalate Issue", data={"key": "value"}, app_version=1, assignee="user@example.com"))
+```
+
+For a practical implementation of the `CreateAction` model, refer to the [action-center-hitl-agent](https://github.com/UiPath/uipath-llamaindex-python/tree/main/samples/action-center-hitl-agent). This sample demonstrates how to create an action with dynamic input.
+
+
+---
+
+### 2. WaitAction
+
+The `WaitAction` model is used to wait for an action to be handled. This model is intended for scenarios where the action has already been created.
+
+#### Attributes:
+
+-   **action** (Action): The instance of the action to wait for.
+
+#### Example:
+
+```python
+from uipath_llamaindex.models import WaitActionEvent
+action_output = ctx.write_event_to_stream(WaitActionEvent(action=my_action_instance))
+```
+
+---
+
+> 💡 UiPath LlamaIndex sdk also supports **Robot/Agent-in-the-loop** scenarios. In this context, the execution of one agent
+> can be suspended until another robot or agent finishes its execution.
+
+### 3. InvokeProcess
+
+The `InvokeProcess` model is utilized to invoke a process within the UiPath cloud platform.
+This process can be of various types, including API workflows, Agents or RPA automation.
+Upon completion of the invoked process, the current agent will automatically resume execution.
+
+#### Attributes:
+
+-   **name** (str): The name of the process to invoke.
+-   **input_arguments** (Optional[Dict[str, Any]]): A dictionary containing the input arguments required for the invoked process.
+
+#### Example:
+
+```python
+from uipath_llamaindex.models import InvokeProcessEvent
+process_output = ctx.write_event_to_stream(InvokeProcessEvent(name="MyProcess", input_arguments={"arg1": "value1"}))
+```
+
+For a practical implementation of the `InvokeProcess` model, refer to the [multi-agent sample](https://github.com/UiPath/uipath-llamaindex-python/tree/main/samples/multi-agent). This sample demonstrates how to invoke a process with dynamic input arguments, showcasing the integration of the interrupt functionality within a multi-agent system or a system where an agent integrates with RPA processes and API workflows.
+
+---
+
+### 4. WaitJob
+
+The `WaitJob` model is used to wait for a job completion. Unlike `InvokeProcess`, which automatically creates a job, this model is intended for scenarios where
+the job has already been created.
+
+#### Attributes:
+
+-   **job** (Job): The instance of the job that the agent will wait for. This should be a valid job object that has been previously created.
+
+#### Example:
+
+```python
+from uipath_llamaindex.models import WaitJobEvent
+job_output = ctx.write_event_to_stream(WaitJobEvent(job=my_job_instance))
+```