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"
The added functions enable mixing colors and manipulating the opacity
of colors and brushes.
They enable the behavior of some of the available functions from SASS and are
added for future use for adding the Adwaita style (future PR).
