chore: update flake.nix and README.md for v0.4.0

Author: github-actions[bot]

README.md

@@ -24,15 +24,15 @@ Using [Devbox](https://www.jetify.com/devbox):
 
 <!-- begin:devbox_install - DON'T EDIT: This block will be replaced by CI -->
 ```bash
-devbox add github:appthrust/karg/v0.3.0#karg
+devbox add github:appthrust/karg/v0.4.0#karg
 ```
 <!-- end:devbox_install -->
 
 Using [Nix](https://nixos.org/):
 
 <!-- begin:nix_install - DON'T EDIT: This block will be replaced by CI -->
 ```bash
-nix run github:appthrust/karg/v0.3.0#karg -- --help
+nix run github:appthrust/karg/v0.4.0#karg -- --help
 ```
 <!-- end:nix_install -->
 

flake.nix

@@ -11,23 +11,23 @@
       let
         pkgs = import nixpkgs { inherit system; };
 
-        version = "0.3.0"; #version - This line is replaced by CI
+        version = "0.4.0"; #version - This line is replaced by CI
 
         assetName = "karg-v${version}-${system}.tar.gz";
 
         # Hashes for each platform (will be updated by CI)
         hashes = {
           "x86_64-linux" = {
-            hash = "sha256:c63f71ef802648cb85f108061b5d133788042e6118ab843772f6c22fe7a773e7"; #x86_64-linux - This line is replaced by CI
+            hash = "sha256:480230d06b3b3dde45d9f8fdfc2a763b68c90d4872bbf07959ff306d9c4cbf2c"; #x86_64-linux - This line is replaced by CI
           };
           "aarch64-linux" = {
-            hash = "sha256:de3cad7f11cb3a8576da5121042ab4b947a901622d1d56439df9d7dda747cc72"; #aarch64-linux - This line is replaced by CI
+            hash = "sha256:e30a16143fb29a5645a7fd19cf67c562d1cbc06ce7e603b102e27d68ab97d156"; #aarch64-linux - This line is replaced by CI
           };
           "x86_64-darwin" = {
-            hash = "sha256:e5683546650f030ffd546bbb4b1bae1306e4c3b0f2c26cd7d88a1fea055f755b"; #x86_64-darwin - This line is replaced by CI
+            hash = "sha256:50fcaacc230fec915c48283928689c386ac3a07470ee987e804061e88f081012"; #x86_64-darwin - This line is replaced by CI
           };
           "aarch64-darwin" = {
-            hash = "sha256:db0efbb14d8128222a9c5c28e32376dfa198bd7114dabb5b9a0e4587d6cda1e3"; #aarch64-darwin - This line is replaced by CI
+            hash = "sha256:521e87b47602750b9b7ebe17e9c21728e3cbd1a7a514a27c06de2744ec83ba63"; #aarch64-darwin - This line is replaced by CI
           };
         };