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"
If the last position expression is invalid due to an unrelated error,
the code that tries to do the interpolation was panicking with the
message "The last should never be invalid". (Because it assumed that
invalid meant that it was not set, and we added a 100% for that last
one if it wasn't set. But if it is set and invalid, this would error.)
