Move from features to option based configuration

modules/nix/common.nix

@@ -0,0 +1,58 @@
+{ lib
+, pkgs
+, localPackages
+, config
+, ...
+}: 
+
+with lib; let 
+    cfg = config.simmer.common;
+in
+{
+
+    options.simmer.common = {
+        neovim.enable = mkOption {
+            description = "Whether to install neovim and set as default editor";
+            type = types.bool;
+            default = true;
+        };
+        
+        nil.enable = mkOption {
+            description = "Whether to install nil";
+            type = types.bool;
+            default = false;
+        };
+
+        shell = mkOption {
+            description = "Default shell to use (fish)";
+            type = types.enum [ "fish" ];
+            default = "fish";
+        };
+    };
+
+
+    config = {
+
+        environment.systemPackages = with pkgs; [
+            curl
+            wget
+            git
+            killall
+            vim
+            eza
+            ripgrep
+            fzf
+            ncdu
+            btop
+        ]
+        ++ optional cfg.nil.enable nil;
+
+        programs.neovim = mkIf cfg.neovim.enable {
+            enable = true;
+            defaultEditor = true;
+        };
+
+        programs.fish.enable = mkIf (cfg.shell == "fish") true;
+    };
+
+}