add copy button to playground

Author: dvdvgt

_sass/light-style/_code.scss

@@ -55,7 +55,7 @@ pre {
       background: none;
       border: none
     }
-    button.button-run:before, button.button-edit:before, button#button-share:before button#button-copy:before {
+    button.button-run:before, button.button-edit:before, button#button-share:before, button#button-copy:before {
       font-family: "Font Awesome 5 Free";
       font-weight: 900;
       padding-right: 0.5em;

flake.nix

@@ -0,0 +1,70 @@
+{
+  description = "Jekyll development environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    flake-utils.url = "github:numtide/flake-utils";
+  };
+
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = nixpkgs.legacyPackages.${system};
+        ruby = pkgs.ruby_2_7;
+        
+        # Automatically generate gemset.nix if needed
+        gems = if builtins.pathExists ./gemset.nix
+          then pkgs.bundlerEnv {
+            name = "jekyll-env";
+            inherit ruby;
+            gemdir = ./.;
+          }
+          else null;
+      in
+      {
+        devShells.default = pkgs.mkShell {
+          buildInputs = with pkgs; [
+            ruby
+            bundler
+            bundix
+            nodejs_20
+          ] ++ (if gems != null then [ gems gems.wrappedRuby ] else []);
+
+          shellHook = ''
+            echo "Jekyll development environment loaded!"
+            echo "Ruby version: $(ruby --version)"
+            echo ""
+            
+            # Check if gemset.nix exists
+            if [ ! -f gemset.nix ]; then
+              echo "⚠️  gemset.nix not found!"
+              echo "Generating Gemfile.lock and gemset.nix..."
+              echo ""
+              
+              # Generate Gemfile.lock if it doesn't exist
+              if [ ! -f Gemfile.lock ]; then
+                bundle lock
+              fi
+              
+              # Generate gemset.nix
+              bundix
+              
+              echo ""
+              echo "✅ Generated gemset.nix successfully!"
+              echo "Please exit and re-enter the shell: exit && nix develop"
+              echo ""
+            else
+              echo "Jekyll version: $(jekyll --version)"
+              echo ""
+              echo "Quick start commands:"
+              echo "  jekyll serve - Start development server"
+              echo "  jekyll build - Build the site"
+              echo ""
+              echo "To update gems after changing Gemfile:"
+              echo "  bundle lock && bundix"
+            fi
+          '';
+        };
+      }
+    );
+}