chore(scripts): add flt-regular to the downstream repositories (#31002)

This is an important project depending on Mathlib, we should have it in the list of downstream repositories.

Co-authored-by: Anne C.A. Baanen <vierkantor@vierkantor.com>

Author: Vierkantor

scripts/downstream_repos.yml

@@ -45,6 +45,12 @@
     build: build-project.yml
     docs: blueprint.yml
     release-tag: create-release.yml
+- github: https://github.com/leanprover-community/flt-regular
+  default_branch: master
+  name: Fermat's Last Theorem for regular primes
+  workflows:
+    build: push.yml
+    docs: push.yml
 - github: https://github.com/leanprover-community/sphere-eversion
   default_branch: master
   name: The sphere eversion project