update flake

Author: BennoLossin

flake.lock

@@ -1,7 +1,16 @@
 {
+  nixConfig = {
+    extra-substituters = [
+      "https://nix-community.cachix.org"
+    ];
+    extra-trusted-public-keys = [
+      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+    ];
+  };
+
   inputs = {
     fenix = {
-      url = "github:nix-community/fenix";
+      url = "github:nix-community/fenix/staging";
       inputs.nixpkgs.follows = "nixpkgs";
     };
     nixpkgs.url = "nixpkgs/nixos-unstable";