Added .sc filename extension for Scala source code, as it is occasionally used
requested to merge digital-diplomat/shared-mime-info:digital-diplomat-master-patch-53278 into master
As a general rule, filename extensions longer than 3 or 4 characters can appear particularly clunky and unwieldly. As such, there are some text editors and programs that recognize .sc as a filename extension for Scala source code. Adding this change to cut down on the extra clutter of lengthier filename extensions.