Add Fortitude to package index (#519)

Author: LiamPattinson

data/package_index.yml

@@ -453,6 +453,13 @@
   categories: programming scientific
   tags: formatter compiler transformer
 
+- name: Fortitude
+  github: PlasmaFAIR/fortitude
+  description: A fast Ruff-like linting tool
+  categories: programming
+  license: MIT
+  tags: linter
+
 # --- Data types ---
 
 - name: Fortran template library