adding fortitude linter and github action

[pmocz]

The fortitude linter can catch some important Fortran errors, and help clean up code and meet modern Fortran standards. It is installable via pip: pip install fortitude-lint and can be run in the terminal in this project as:

fortitude check --file-extensions=fypp

There is a fortitude.toml file that sets some extra configurations and errors to ignore.

Check it out if you'd like! Right now I disabled some of the checks in the .toml file because there are a bunch to potentially fix. But it is applying some formatting fixes. Fortitude can fix some errors automatically by adding the --fix flag when calling it in the command line

I also added a github action that will always perform static analysis on the code

Feel free to merge if you think this could be useful, or ignore if not.