update docs: py_trees_ros_viewer (#15)

docs/how_to_run.rst

@@ -29,6 +29,59 @@ information of py_trees and parser:
    ros2 run scenario_execution scenario_execution $(PATH_TO_SCENARIO_FILE) -t -d
 
 
-Using RVIZ to trigger scenario
-------------------------------
+Visualize Scenario with PyTrees ROS Viewer
+------------------------------------------
 
+Before getting started, ensure that the PyQt5 version 5.14 Python library is installed. You can check PyQt5 version using the following command:
+
+.. code-block:: bash
+
+   pip freeze | grep -i pyqt
+
+If any PyQt5 libraries are detected, it's recommended to uninstall them to avoid conflicts:
+
+.. code-block:: bash
+
+   pip3 uninstall PyQt5 PyQt5-Qt5 PyQt5-sip PyQtWebEngine PyQtWebEngine-Qt5
+
+Additionally, if the default PyQtWebEngine is present, remove it using:
+
+.. code-block:: bash
+
+   sudo apt remove python3-pyqt5.qtwebengine
+
+Next, install PyQt and PyQtWebEngine version 5.14:
+
+.. code-block:: bash
+
+   pip install PyQt5==5.14
+   pip install PyQtWebEngine==5.14
+
+Once PyQt is set up, clone the ``py_trees_ros_viewer`` repository:
+
+.. code-block:: bash
+
+   git clone git@github.com:splintered-reality/py_trees_ros_viewer.git
+
+After cloning, build the package using ``colcon build`` and source the workspace.
+
+Now, to open the viewer, execute the following command:
+
+.. code-block:: bash
+
+   py-trees-tree-viewer --no-sandbox
+
+Finally, in a separate terminal, run the scenario file to visualize the behavior tree.
+
+Example:
+
+.. code-block:: bash
+
+      ros2 launch scenario_execution scenario_launch.py scenario:=examples/example_scenario/hello_world.osc
+
+.. figure:: images/py_tree_viewer.png
+   :alt: Behavior Tree Viewer 
+
+
+Please note that this method has been tested on Ubuntu 22.04. If you are using any other distribution, please ensure that 
+PyQtEngine works on your machine and render web pages correctly.