chore: use version from project in flake

flake.nix

@@ -48,10 +48,14 @@
 
       packages = forAllSystems (
         { pkgs }:
+        let
+          project_file = builtins.readFile ./project.godot;
+          version = builtins.head (builtins.match ".*version=\"([0-9.]+)\".*" project_file);
+        in
         {
           slopvivors = pkgs.stdenv.mkDerivation {
             pname = "slopvivors";
-            version = "0.1.0";
+            version = version;
             src = ./.;
 
             strictDeps = true;
@@ -82,7 +86,7 @@
           };
           slopvivors_web_files = pkgs.stdenv.mkDerivation {
             pname = "slopvivors-web-files";
-            version = self.packages.${pkgs.system}.slopvivors.version;
+            version = version;
             src = ./.;
 
             strictDeps = true;
@@ -112,7 +116,7 @@
           };
           slopvivors_web = pkgs.buildGoModule {
             pname = "slopvivors-web";
-            version = self.packages.${pkgs.system}.slopvivors_web.version;
+            version = version;
             vendorHash = null;
             src = self.packages.${pkgs.system}.slopvivors_web_files;
 
@@ -155,7 +159,7 @@
           };
           slopvivors_docker = pkgs.dockerTools.buildLayeredImage {
             name = "slopvivors-docker";
-            tag = "${self.packages.${pkgs.system}.slopvivors.version}";
+            tag = version;
             created = "now";
             contents = [
               pkgs.busybox