docs: show licenses in UI

This adds a button to the header that opens a dialog that shows all
licenses and third-party licenses.

Author: Tigge

.pnp.js

@@ -67,6 +67,9 @@ packageExtensions:
     dependencies:
       react: '*'
       react-dom: '*'
+  license-webpack-plugin@*:
+    dependencies:
+      webpack: '*'
 
 plugins:
   - path: .yarn/plugins/@yarnpkg/plugin-interactive-tools.cjs