Update my_application.cc

[s-b-repo]

Key Changes:

KDE Detection: The code now checks for KDE's window manager, KWin, to avoid using a GNOME-style header bar when the app is running in KDE.
Window Title Bar: If not running in GNOME or KDE, the app will use a traditional window title bar instead of the GNOME header bar.

[s-b-repo]

Header Comments: Added more detailed comments to explain what the MyApplication struct is and what the my_application_new() function does. This makes the file more informative for future maintainers or anyone unfamiliar with the code.

Documentation of Return Value: Added (transfer full) annotation in the function documentation, which follows the GObject Introspection conventions. This indicates that the caller takes ownership of the returned value and is responsible for freeing it.

General Formatting: Improved spacing and alignment for readability. The header guards and function prototypes are easier to read and maintain.

[NANI-SORE]

Please move build instructions to a separate file (something like build_linux.md). Since we stopped doing desktop builds for now we don't need linux build instructions in main readme