docs: update learning.mdx (testing-library#891)

Author: andrewarosario

docs/learning.mdx

@@ -50,6 +50,8 @@ sidebar_label: Learning Material
   by [Pablo Dinella](https://github.com/PabloDinella)
 - [React Hooks broke my tests, now what? (Portuguese)](https://youtu.be/t46n7REGswQ?t=99)
   by [Daniel Afonso](https://twitter.com/danieljcafonso)
+- [Escrevendo testes eficientes de verdade no Angular](https://andrewrosario.medium.com/escrevendo-testes-eficientes-de-verdade-no-angular-263a9d03cecf)
+  by [Andrew Rosário](https://github.com/andrewarosario)
 
 ## Spanish 🇪🇸