Add ufla-normas extension to listings (#2310)

* Add duolingo and ufla-normas extensions to listings

* Remove duolingo from listings

Author: bonijoao

docs/extensions/listings/custom-formats.yml

@@ -177,3 +177,11 @@
   author: '[Fred Guth](https://github.com/fredguth/)'
   description: |
     Manuscript template inspired by the style of the books from Edward R. Tufte
+
+- name: ufla-normas
+  path: https://github.com/bonijoao/ufla-normas
+  author: '[João Bonifácio](https://github.com/bonijoao)'
+  description: >
+    PDF format for theses and dissertations following the academic writing
+    standards of the Universidade Federal de Lavras (UFLA, Brazil), 6th edition
+    (2025), with ABNT author-date citations.