Updated the version from 1.1 to 1.2
Renamed the header to "Slint Royalty-free Desktop, Mobile, and Web Applications License"
Added definition of "Mobile Application" and grant of right
Moved "Limitations" to 3rd section and "License Conditions - Attributions" to 2nd section
Added flexibility to choose between showing "MadeWithSlint" as a dialog/splash screen or on a public webpage
Moved the para on copyright notices to section under "Limitations"
This provides a Model base class in Python and sub-classes of that
can be set as data models in slint.
The ListModel is provided as basic sub-class operating on a list() and
allowing mutation and notifying the view on the Slint side.
Similarly, an array declared in Slint is exposed as an object to Python
that looks like a Model.
Both support the sequence protocol.
Fixes#4135
