Unity package that adds item template for Unity Class with namespace, AddComponentMenu attribute, and extends MonoBehaviour class. Also removes Assets.Scripts from namespace for better nameing.
Also, there is a Visual Studio extension with the same tool.
- Unity 2019 or higher
- Open the Package Manager from Window > Package Manager
- "+" button > Add package from git URL
- Enter the following to install
Now you can create a file via top menu:

Alternatively, right-click on the project window context. Create -> C# Script with namespace