Add Differentia package to index (#557)

* Add Differentia package to index

* Implement @ivan-pi suggestion from code review

Co-authored-by: Ivan Pribec <ivan.pribec@gmail.com>

---------

Co-authored-by: Ivan Pribec <ivan.pribec@gmail.com>

Author: niccolozanotti

data/package_index.yml

@@ -393,6 +393,14 @@
   license: MIT
   version: 3.16-v2
 
+- name: Differentia
+  github: Nicholaswogan/Differentia
+  description: Computes derivatives, gradients and Jacobians of Fortran functions/subroutines using forward automatic differentiation.
+  categories: programming numerical
+  tags: algorithmic derivative AD autodiff
+  license: MIT
+  version: 0.1.4
+
 - name: camfort
   github: camfort/camfort
   description: Light-weight verification and transformation tools for Fortran