Add Tim McNamara's article about Deref to Step 1.5

1_concepts/1_5_convert_cast_deref/README.md

@@ -140,6 +140,7 @@ hello(&m);
 For better understanding [`Deref`] purpose, design, limitations and use cases read through:
 - [Rust Book: 15.2. Treating Smart Pointers Like Regular References with the Deref Trait][3]
 - [Official `Deref` docs][`Deref`]
+- [Tim McNamara: Explaining Rust’s Deref trait][13]
 
 
 ### Incorrect usage
@@ -227,3 +228,4 @@ After completing everything above, you should be able to answer (and understand
 [10]: https://ricardomartins.cc/2016/08/03/convenient_and_idiomatic_conversions_in_rust
 [11]: https://rust-lang.github.io/rust-clippy/master/index.html#as_conversions
 [12]: https://rusty-ferris.pages.dev/blog/asref-vs-borrow-trait
+[13]: https://timclicks.dev/explaining-rusts-deref-trait