Fix artifact name

frontend/package.json

@@ -18,7 +18,7 @@
     "build": "react-scripts build",
     "test": "react-scripts test",
     "eject": "react-scripts eject",
-    "compress": "tar -czvf $npm_package_name_v$npm_package_version.tar.gz build/*" 
+    "compress": "tar -czvf ${npm_package_name}_v${npm_package_version}.tar.gz build/*" 
   },
   "eslintConfig": {
     "extends": [