Examples Using Drupal Content

Problem/Motivation

Add examples to the islands_example module that show how Drupal content can be used with the islands element. Things like:
* Rendering Drupal content as the server rendered pre-js fallback.
* Passing Drupal data as props to the hydrated framework component.
* Passing Drupal data as slots to the hydrated framework component.

Proposed resolution

Seems likely that this will inspire some helpers or additional features in the main islands module. We might want to split those out into standalone issues.