This example shows how to create a context menu for your application.
It demonstrates window level and global context menus.
A simple menu is registered with the window and the application with the id "test".
In our frontend html, we then use the --custom-contextmenu style to attach the menu to an element.
We also use the --custom-contextmenu-data style to pass data to the menu callback which can be read in Go.
This is really useful when using components to distinguish between different elements.