Adding Fortran Error Handler

[samharrison7]

I've just fpm-ified my Fortran error handler and so thought it would be a good time to add it here. I've also created a separate PR over at fortran-lang.org: fortran-lang/fortran-lang.org#356 (is that the way to do it, or should I have just created one PR?)

I also spotted a broken link in the README so have fixed that here.

[samharrison7]

Can't figure why the build is failing, the error doesn't give much away... Only thing I can think of is that the "name" defined in fpm.toml is feh, whilst I've called it fortran-error-handler here? Also it seems to be not just my package it's failing on.

[awvwgk]

The copyright keyword is probably missing for the currently implemented checks. See #24 for a discussion on the required keywords.

[samharrison7]

Thanks @awvwgk, adding copyright seems to have done the trick!