Add ffmt - fast Fortran formatter written in Rust

[sbryngelson]

Adds ffmt to the Fortran formatters.

ffmt is a fast, configurable Fortran formatter written in Rust, installable via pip. Key features:

• Indentation, whitespace normalization, keyword casing, line wrapping
• Operator modernization (.eq. → ==), double-colon enforcement
• Comment rewrapping, inline spacing, !< alignment
• Preprocessor support: Fypp, C preprocessor, OpenACC, OpenMP
• Opt-in: multi-statement splitting, assignment alignment, use-statement reformatting
• LSP support, parallel formatting (-j N), stdin/stdout, CI check mode (--check)

MIT licensed, actively maintained, 20+ stars.

[mre]

Can you rebase your PR on top of master to trigger your new PR workflow?

[github-actions]

Contributing criteria check

[FAIL] ffmt

Source: https://github.com/sbryngelson/ffmt

Criterion	Result
Stars (min 20)	fail 1 stars (minimum is 20)
Contributors (min 2)	fail 1 contributor(s) (minimum is 2)
Age (min 3 months)	fail created 22 days ago, needs 68 more days to meet the 3-month minimum

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One or more tools do not meet the contributing criteria yet. We will keep this PR open. Feel free to update it once the thresholds are met.