Add Fortran

[cyrusmsk]

I think Fortran has everything required to implement this problem efficiently:

• JSON library: https://github.com/jacobwilliams/json-fortran
• Std HashMap: https://stdlib.fortran-lang.org/page/specs/stdlib_hashmaps.html
• Other HashMap implementations are also available

I've used Fortran many years ago in the University. We used Fortran 90/95. But for this problem I suppose is better suit something modern like 2008/2018 standard.

I hope someone familiar with modern Fortran will be interested to contribute the solution :)