Add Guillem L. Jara's article about dyn dispatch and unions to Step 1.6

1_concepts/1_6_dispatch/README.md

@@ -147,6 +147,13 @@ There is a handy [momo] crate, which generates this boilerplate automatically in
 
 
 
+## More reading
+
+- [Guillem L. Jara: Designing an efficient memory layout in Rust with unsafe & unions, or, an overlong guide in avoiding dynamic dispatch][21]
+
+
+
+
 ## Task
 
 Given the following `Storage` abstraction and `User` entity:
@@ -201,3 +208,4 @@ After completing everything above, you should be able to answer (and understand
 [18]: https://lucumr.pocoo.org/2022/1/6/rust-extension-map
 [19]: https://lucumr.pocoo.org/2022/1/7/as-any-hack
 [20]: https://medium.com/digitalfrontiers/rust-dynamic-dispatching-deep-dive-236a5896e49b
+[21]: https://alonely0.github.io/blog/unions