"About the program" dialog
Unfortunately, currently NiGui does not have a template for creating an "About" dialog. `window.alert()` and `window.msgBox()` do not allow you to adjust the font size, centering, set the icon, so I would really like to be able to create the "About" dialog, blocking the accessibility of the main window during display.
Here's an example from GTK+:
![image](https://user-images.githubusercontent.com/43933400/103917502-ba377f00-511e-11eb-9e36-582614a93a04.png)
