feat(v2): debug pages + debug layout + ability to debug content (#3229)

* improve debug plugin:
- add multiple debug pages + debug layout
- ability to debug plugin contentLoaded data

* add missing dependency

* fix broken test

* improve content rendering a bit

* create basic DebugJsonView

* fix ReactJson SSR issues

website/docusaurus.config.js

@@ -156,6 +156,7 @@ module.exports = {
     [
       '@docusaurus/preset-classic',
       {
+        debug: true, // force debug plugin usage
         docs: {
           // routeBasePath: '/',
           path: 'docs',