Add zed-editor package and overlay to flake (#16783)

Adds a `zed-editor` package to the flake, along with exported overlay.
Uses [`crane`](https://crane.dev) to avoid issues with updating
git-sourced dependencies' hashes. Crane will also be useful if we want
to export separate packages for `stable`, `preview`, and `nightly` in
the future.

Release Notes:

- Added a default package + overlay to Zed's Nix flake. This is useful
for users wanting to pilot nightly builds of Zed on NixOS.

shell.nix

@@ -1,57 +1,14 @@
-{
-  pkgs ? import <nixpkgs> { },
-}:
-
-let
-  stdenv = pkgs.stdenvAdapters.useMoldLinker pkgs.llvmPackages_18.stdenv;
-in
-if pkgs.stdenv.isDarwin then
-  # See https://github.com/NixOS/nixpkgs/issues/320084
-  throw "zed: nix dev-shell isn't supported on darwin yet."
-else
-  (pkgs.mkShell.override { inherit stdenv; }) rec {
-    nativeBuildInputs = with pkgs; [
-      copyDesktopItems
-      curl
-      perl
-      pkg-config
-      protobuf
-      rustPlatform.bindgenHook
-    ];
-
-    buildInputs = with pkgs; [
-      curl
-      fontconfig
-      freetype
-      libgit2
-      openssl
-      sqlite
-      zlib
-      zstd
-
-      alsa-lib
-      libxkbcommon
-      wayland
-      xorg.libxcb
-    ];
-
-    env = {
-      LD_LIBRARY_PATH =
-        with pkgs;
-        lib.makeLibraryPath (
-          buildInputs
-          ++ [
-            stdenv.cc.cc.lib
-            vulkan-loader
-          ]
-        );
-      ZSTD_SYS_USE_PKG_CONFIG = true;
-      FONTCONFIG_FILE = pkgs.makeFontsConf {
-        fontDirectories = [
-          "assets/fonts/zed-mono"
-          "assets/fonts/zed-sans"
-        ];
-      };
-      PROTOC = "${pkgs.protobuf}/bin/protoc";
-    };
-  }
+(
+  import
+  (
+    let
+      lock = builtins.fromJSON (builtins.readFile ./flake.lock);
+    in
+      fetchTarball {
+        url = lock.nodes.flake-compat.locked.url or "https://github.com/edolstra/flake-compat/archive/${lock.nodes.flake-compat.locked.rev}.tar.gz";
+        sha256 = lock.nodes.flake-compat.locked.narHash;
+      }
+  )
+  {src = ./.;}
+)
+.shellNix