Add link to nix develop man page

sevanspowell · sevanspowell · commit e6bbfe10bcff · 2022-02-16T12:49:30.000+08:00
diff --git a/docs/code/Flakes/Tutorials/Hacking.md b/docs/code/Flakes/Tutorials/Hacking.md
@@ -31,3 +31,7 @@ order: 3
 ```
 
 We could then run `nix develop` and we would enter a shell with access to python.
+
+## Reference
+
+[nix develop man page](https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-develop.html)
