README: Add reference to dev/README.md

Signed-off-by: Hanno Becker <beckphan@amazon.co.uk>

Author: hanno-becker

README.md

@@ -81,7 +81,7 @@ PR.
 
 Our AArch64 assembly is developed using [SLOTHY](https://github.com/slothy-optimizer/slothy): We write
 'clean' assembly by hand and automate micro-optimizations (e.g. see the [clean](dev/aarch64_clean/src/ntt_clean.S)
-vs [optimized](mlkem/native/aarch64/src/ntt_opt.S) AArch64 NTT).
+vs [optimized](mlkem/native/aarch64/src/ntt_opt.S) AArch64 NTT). See [dev/README.md](dev/README.md) for more details.
 
 ## How should I use mlkem-native?