Use external JuliaFormatter in Zed config

Zed and the Julia LSP seem to be arguing a
lot lately, and that breaks my blue-styled
code. Use the JuliaFormatter as an external
command to get code formatting on save even
when the Julia LSP crashes.

pkgs.nix

@@ -10,6 +10,7 @@
     git-absorb
     gnugrep
     gnused
+    gzip
     htop
     jq
     julia-bin

programs/zed.nix

@@ -12,6 +12,7 @@
     "latex"
     "macos-classic"
     "nix"
+    "r"
     "toml"
     "xml"
   ];
@@ -27,6 +28,17 @@
     buffer_font_size = 11;
     features = { edit_prediction_provider = "zed"; };
     languages = {
+      Julia = {
+        formatter = {
+          external = {
+            command = "julia";
+            arguments = [
+              "-e"
+              "using JuliaFormatter; print(format_text(String(read(stdin))));"
+            ];
+          };
+        };
+      };
       Nix = { formatter = { external = { command = "nixfmt"; }; }; };
     };
     preview_tabs = { enabled = false; };