add compress image function

flake.nix

@@ -9,12 +9,24 @@
       default = pkgs.mkShell {
         packages = with pkgs; [
           zola
+          imagemagick
           (writeShellScriptBin "serve" ''
             zola serve --open
           '')
           (writeShellScriptBin "build" ''
             zola build
           '')
+          (writeShellScriptBin "compress-images" ''
+            if [ -z "$1" ]; then
+              echo "Usage: compress-images <folder>"
+              exit 1
+            fi
+            find "$1" -type f \( -iname '*.png' -o -iname '*.jpg' -o -iname '*.jpeg' \) | while read -r img; do
+              outfile="''${img%.*}.webp"
+              ${imagemagick}/bin/magick "$img" -resize '1800>' -quality 82 "$outfile"
+              echo "Converted: $img -> $outfile"
+            done
+          '')
         ];
         shellHook = ''
           echo "Zola blog development environment"