add prettier and docs-check script

package.json

@@ -50,6 +50,7 @@
         "jszip": "^3.7.1",
         "manifold-3d": "^2.5.1",
         "moment": "^2.29.4",
+        "prettier": "^3.5.3",
         "react-responsive-carousel": "^3.2.23",
         "serve-static": "^1.14.1",
         "three": "^0.174.0",
@@ -98,7 +99,8 @@
         "preinstall": "node bin/install-pre.js && npx webpack --config bin/webpack-three.js",
         "docs-dev": "docusaurus start",
         "docs-build": "docusaurus build",
-        "docs-serve": "docusaurus serve"
+        "docs-serve": "docusaurus serve",
+        "docs-check": "prettier ./docs --check"
     },
     "main": "app-el.js",
     "build": {