Made by UmKraLegal
Put the stopwatch folder inside your project's addons folder, (create if none)
Then Project -> Project Settings -> Plugins and enable Stopwatch plugin
Code based on original timer.cpp file (MIT license)
https://github.com/godotengine/godot/blob/8b692e88726bb7ab114a3a0b1b2ffd973dd4f054/scene/main/timer.cpp
Icon based on original Godot Node.svg
https://github.com/godotengine/godot/blob/master/editor/icons/Node.svg