Add ROS 2 Actions for Asynchronous Tasks article (#161)

Introduces a comprehensive guide on implementing asynchronous action servers in ROS 2.

- Explains the differences between Services, Pub/Sub, and Actions.
- Provides a basic skeleton for ROS 2 Python Action Servers and Clients.
- Details a "Mission Control" example to demonstrate non-blocking execution using ReentrantCallbackGroups, MultiThreadedExecutors, and threading events.
- Alphabetizes the Programming section in navigation.yml for improved discoverability.
- Fixes several markdown standards violations (alt text, code block tags).

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Co-authored-by: Nevin Valsaraj <nevin.valsaraj32@gmail.com>

Author: sushanthj

_data/navigation.yml

@@ -262,24 +262,26 @@ wiki:
         url: /wiki/programming/boost-library/
       - title: Boost Maps and Vectors
         url: /wiki/programming/boost-maps-vectors/
+      - title: Building Software from Source
+        url: /wiki/programming/build-from-source/
       - title: Cmake
         url: /wiki/programming/cmake/
       - title: Eigen Library
         url: /wiki/programming/eigen-library/
       - title: Git
         url: /wiki/programming/git/
-      - title: Programming Interviews
-        url: /wiki/programming/google-programming-interviews/
       - title: Multithreaded Programming
         url: /wiki/programming/multithreaded-programming/
+      - title: Programming Interviews
+        url: /wiki/programming/google-programming-interviews/
       - title: Programming Tutorials and Resources
         url: /wiki/programming/tutorials-resources/
       - title: Python Construct
         url: /wiki/programming/python-construct/
-      - title: Building Software from Source
-        url: /wiki/programming/build-from-source/
       - title: ROS 2 Yasmin State Machine
         url: /wiki/programming/yasmin-ros2-state-machine/
+      - title: ROS2 Action Servers for Asynchronous Tasks
+        url: /wiki/programming/ros2-async-action-servers/
   - title: Networking
     url: /wiki/networking/
     children: