Update npm build to include jupyter lab extension build

Author: marthacryan

plotly/labextension/package.json

@@ -5,7 +5,8 @@
   "scripts": {
     "build:widget": "esbuild --bundle --alias:plotly.js=plotly.js/dist/plotly --format=esm --minify --outfile=../package_data/widgetbundle.js src/widget.ts",
     "build:mimerenderer": "esbuild --bundle --alias:plotly.js=plotly.js/dist/plotly --format=esm --minify --outfile=lib/mimeExtension.js src/mimeExtension.ts",
-    "build": "npm run build:widget && npm run build:mimerenderer",
+    "build:labextension": "jupyter labextension build .",
+    "build": "npm run build:widget && npm run build:mimerenderer && npm run build:labextension",
     "watch": "npm run build -- --watch --sourcemap=inline",
     "typecheck": "tsc --noEmit"
   },