Update package.json

fixed the `build:py`, the metadata_path needed to be explicitely given. It works on windows 10

Author: Bachibouzouk

package.json

@@ -7,7 +7,7 @@
     "start": "webpack-serve ./webpack.serve.config.js --open",
     "build:js-dev": "webpack --mode development",
     "build:js": "webpack --mode production",
-    "build:py": "node ./extract-meta src/lib/components > my_dash_component/metadata.json && copyfiles package.json my_dash_component",
+    "build:py": "node ./extract-meta src/lib/components > my_dash_component/metadata.json && copyfiles package.json my_dash_component && python -c \"import dash; dash.development.component_loader.generate_classes('my_dash_component', 'my_dash_component/metadata.json')\"",
     "build:all": "npm run build:js & npm run build:py",
     "build:all-dev": "npm run build:js-dev & npm run build:py"
   },