Add new icons for Fortran source code
Following up on https://bugs.kde.org/show_bug.cgi?id=456961
At the moment Fortran source code does not have an icon, and instead uses the generic text one.
In this commit I am preposing some new icons to fix this.
As mentioned in the initial bug report, the 'F' in the icon is taken from the logo of https://fortran-lang.org/ Their licence for the logo seems to be MIT though their is some discussion about moving it to CC-BY-NC-SA ( https://github.com/fortran-lang/fortran-lang.org/issues/342 )
Thanks