chore: uiv2 docz custom page (#1511)

* feat: Customized Docz Layout

* manually apply padding into playground

* fix playground bug -- sticky items

* fix window

* remove specifc tailwind style for docz

platform/ui/package.json

@@ -27,9 +27,12 @@
   "dependencies": {
     "classnames": "^2.2.6",
     "docz": "^2.2.0",
+    "theme-ui": "^0.2.38",
+    "gatsby": "2.19.24",
     "gatsby-plugin-postcss": "^2.1.20",
     "gatsby-plugin-react-svg": "^3.0.0",
     "gatsby-plugin-sass": "^2.1.28",
+    "gatsby-theme-docz": "^2.2.0",
     "node-sass": "^4.13.1",
     "prop-types": "^15.7.2",
     "react": "^16.11.0",