Add devenv nix

devenv.yaml

@@ -0,0 +1,11 @@
+inputs:
+  git-hooks:
+    url: github:cachix/git-hooks.nix
+    inputs:
+      nixpkgs:
+        follows: nixpkgs
+  treefmt-nix:
+    url: github:numtide/treefmt-nix
+    inputs:
+      nixpkgs:
+        follows: nixpkgs