Revert "Temporarily remove README from code"

This reverts commit 06cef1a.

Author: LegNeato

blog/2024-11-21-optimizing-matrix-mul/code/README.md

@@ -0,0 +1,21 @@
+The Rust code that accompanies the blog post.
+
+<!-- truncate -->
+
+You will find:
+
+1. A binary (`blog`) that you can run with `cargo run`
+2. Benchmarks that you can run with `cargo bench`
+3. GPU shaders/kernels written in Rust
+4. CPU code that takes the shaders and runs it on the GPU (via `wgpu`) or the CPU with a
+   simulated harness
+5. Some tests that you can run with `cargo test`
+
+A good place to start to get the lay of the land is the workspace's `Cargo.toml` in this
+directory.
+
+**Any changes to these files should ensure that the blog post is still correct as it
+uses line numbers to embed code snippets.**
+
+Note: Everything needs to be run with `--release` to work around
+https://github.com/Rust-GPU/rust-gpu/issues/29.