Add support for fortitude

**Name:** fortitude
**URL:** https://github.com/PlasmaFAIR/fortitude

PlasmaFAIR's fortitude is fast syntax checker and linter for contemporary Fortran. Inspired by ruff (for Python), it helps both to identify oddities in the source code, as well as to optionally fix them for the better by a set of community based rules. The tool's action can be adjusted to the user's needs (for instance about rules gradually implemented).

Fortitude already is recognized for instance by the community of [fortran-lang.org](https://fortran-lang.discourse.group/t/fortitude-a-fortran-linter/8834). Its efficiency to work reliably well and fast was presented by its main developers Liam Pattinson and Peter Hill e.g., by their talk on May 22nd, 2025 at a Cambridge University Research Software Engineering Seminar ([youtube recording](https://www.youtube.com/watch?v=gAdgqfq-yxU)). I think it would be nice addition to Ale, complementary to the present checks with gcc.