Provide specialization for qsTr and string.arg()

There is a qmlsc warning produced when trying to make an arg call on qStr.

For example:
qStr("Hello").arg("World")

This will result in the following warning

Warning: main.qml:7:29: Property "arg" not found on type "void"
title: qsTr("Hello %1").arg("World")
^^^

It is suspected that type info for qsTr does not say it returns a string, as someone should be able to call arg() on it. It should be noted that this appears to only occur on linux, could not re-produce this warning on windows.