feat: configure numtide binary cache

Signed-off-by: Brian McGee <[email protected]>

Author: brianmcgee

flake.nix

@@ -1,6 +1,15 @@
 {
   description = "Treefmt: once CLI to format your repo";
 
+  nixConfig = {
+    extra-substituters = [
+      "https://numtide.cachix.org"
+    ];
+    extra-trusted-public-keys = [
+      "numtide.cachix.org-1:2ps1kLBUWjxIneOy1Ik6cQjb41X0iXVXeHigGmycPPE="
+    ];
+  };
+
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
     flake-parts = {