Update dependency docz to v2

Author: renovate-bot

src/frontend/package.json

@@ -103,7 +103,7 @@
         "babel-preset-flow": "6.23.0",
         "cross-env": "5.2.1",
         "css-loader": "3.3.2",
-        "docz": "1.3.2",
+        "docz": "2.2.0",
         "docz-plugin-css": "0.11.0",
         "docz-theme-default": "1.2.0",
         "eslint": "6.7.2",