initial flake with clan cli and formating

shell.nix

@@ -0,0 +1,12 @@
+{ inputs, ... }:
+{
+  perSystem =
+    { system, ... }:
+    {
+      devshells.default = {
+        devshell = {
+          packages = [ inputs.clan-core.packages.${system}.clan-cli ];
+        };
+      };
+    };
+}