issue-193: add shutdown handler for client to call and close alive sockets

[varunverlencar]

Add TCP port socket shutdown if not alive

Public API Changes

Add shutdown handler for clients /shutdown

Description

1. Added changes for shutdown handler and api
2. Added readme usage instructions
3. tested on local javascipt UI

#193

[varunverlencar]

tested with ros2 run image_tools cam2image --ros-args -p frequency:=30.0 -p width:=640 -p height:=480 -p burger_mode:=true
and custom UI that listens on web_video_server: you can also use web-browser http://localhost:8080/shutdown?topic=/image
output:

[INFO] [web_video_server-1]: process started with pid [246966]
[web_video_server-1] [INFO] [1763087236.891895946] [web_video_server]: Waiting For connections on 0.0.0.0:8080
[web_video_server-1] [INFO] [1763087282.546730930] [web_video_server]: Handling Request: /stream?topic=/image
[web_video_server-1] [INFO] [1763087282.547466223] [web_video_server]: Streaming topic /image with QoS profile default
[web_video_server-1] [INFO] [1763087290.387515416] [web_video_server]: Handling Request: /shutdown
[web_video_server-1] [INFO] [1763087290.387721288] [web_video_server]: Shutdown request removed 1 stream(s) for topic <all>
[web_video_server-1] [INFO] [1763087290.388883366] [web_video_server]: Handling Request: /shutdown
[web_video_server-1] [INFO] [1763087290.388922029] [web_video_server]: Shutdown request removed 0 stream(s) for topic <all>
[web_video_server-1] [INFO] [1763087290.393034420] [web_video_server]: Removed Stream: /image
[web_video_server-1] [INFO] [1763087296.019929017] [web_video_server]: Handling Request: /stream?topic=/image
[web_video_server-1] [INFO] [1763087296.020282519] [web_video_server]: Streaming topic /image with QoS profile default
[web_video_server-1] [INFO] [1763087299.776973402] [web_video_server]: Handling Request: /shutdown
[web_video_server-1] [INFO] [1763087299.777058013] [web_video_server]: Shutdown request removed 1 stream(s) for topic <all>
[web_video_server-1] [INFO] [1763087299.778284809] [web_video_server]: Handling Request: /shutdown
[web_video_server-1] [INFO] [1763087299.778319854] [web_video_server]: Shutdown request removed 0 stream(s) for topic <all>
[web_video_server-1] [INFO] [1763087299.892136295] [web_video_server]: Removed Stream: /image