module: add :lang fortran

* feat(fortran): account for f90 and fortran modes

* feat(fortran): initial keybindings

* feat(fortran): basic compilation

* feat(fortran): compilation popup

This customizes the name of the compilation buffer produced by the
`compile` function. We're keeping things simple; Emacs already knows how
to run compilation commands in a popup and parse the results, so let's
let it do its thing.

* feat(fortran): doctor checks

* docs(fortran): installation instructions

* feat(fortran): actual usage of fpm

* feat(fortran): configure compilation popups

* feat(fortran): improved raw gfortran usage

Although it's recommended to do everything through `fpm` to make life
easier.

* docs(fortran): backburner `+intel` for now

* feat(fortran): address PR suggestions

init.example.el

@@ -129,6 +129,7 @@
        ;;ess               ; emacs speaks statistics
        ;;factor
        ;;faust             ; dsp, but you get to keep your soul
+       ;;fortran           ; in FORTRAN, GOD is REAL (unless declared INTEGER)
        ;;fsharp            ; ML stands for Microsoft's Language
        ;;fstar             ; (dependent) types and (monadic) effects and Z3
        ;;gdscript          ; the language you waited for