Add ray tracer part 3 to walkthroughs

Author: bahelms

draft/2023-04-12-this-week-in-rust.md

@@ -49,6 +49,7 @@ and just ask the editors to select the category.
 - [A guide to aid you in your journey of becoming a Rustacean](https://rust-lang.guide/)
 
 * [Flexible Tracing with Rust and OpenTelemetry](https://broch.tech/posts/rust-tracing-opentelemetry/)
+* [Build a Ray Tracer, pt. 3 - Let There Be Light!](https://www.superperfundo.dev/articles/ray-tracer-part3)
 
 ### Research