fix: missing cross-env from build:umd in package.json (#7460)

packages/excalidraw/package.json

@@ -114,7 +114,7 @@
   "homepage": "https://github.com/excalidraw/excalidraw/tree/master/packages/excalidraw",
   "scripts": {
     "gen:types": "tsc --project tsconfig-types.json",
-    "build:umd": "rm -rf dist && cross-env NODE_ENV=production webpack --config webpack.prod.config.js && cross-env NODE_ENV=development webpack --config webpack.dev.config.js && NODE_ENV=development webpack --config webpack.preact.config.js && NODE_ENV=production webpack --config webpack.preact.config.js && yarn gen:types",
+    "build:umd": "rm -rf dist && cross-env NODE_ENV=production webpack --config webpack.prod.config.js && cross-env NODE_ENV=development webpack --config webpack.dev.config.js && cross-env NODE_ENV=development webpack --config webpack.preact.config.js && cross-env NODE_ENV=production webpack --config webpack.preact.config.js && yarn gen:types",
     "build:umd:withAnalyzer": "cross-env NODE_ENV=production ANALYZER=true webpack --config webpack.prod.config.js",
     "pack": "yarn build:umd && yarn pack",
     "start": "webpack serve --config webpack.dev-server.config.js",