add to rust walkthroughs - article on macros in rust part 3 (#7105)

Author: hackeryarn

draft/2025-10-08-this-week-in-rust.md

@@ -54,6 +54,7 @@ and just ask the editors to select the category.
 ### Observations/Thoughts
 
 ### Rust Walkthroughs
+* [Let's write a macro in Rust - Part 3](https://hackeryarn.com/post/rust-macros-3/)
 
 * [Rust/C++ Interop Part 5 - Interop in 2025: A Complete Example](https://tylerjw.dev/posts/20251003-rust-cpp-interop-2025-update/)