build(flake.nix/inputs): Add devshell input and unify it with ethereum-nix.inputs.devshell

Author: PetarKirov

flake.lock

@@ -86,6 +86,7 @@
         flake-compat.follows = "flake-compat";
         treefmt-nix.follows = "treefmt-nix";
         fenix.follows = "fenix";
+        devshell.follows = "devshell";
       };
     };
 
@@ -110,6 +111,13 @@
       };
     };
 
+    devshell = {
+      url = "github:numtide/devshell";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+      };
+    };
+
     cachix = {
       url = "github:cachix/cachix";
       inputs = {