Display non-markdown content in the WYSIWYG mode of the SSE::HTML

Implementation issue for HTML syntax from #216836 (closed)

TODOS

• base implementation (!36250 (merged))
• edge-cases (!36330 (merged))
  • We may want to actually render html blocks in the code editor in some way, but if so we must not change the source to do so. We might be able to just change the token wrapping nodes akin to https://github.com/nhn/tui.editor/blob/6ee6bd65aeccc7efbe7698fec6643a69f65e2af3/apps/editor/docs/custom-html-renderer.md#using-multiple-tags-for-a-node. Next step is to look into this (as it'll solve the <link> issue too.
  • <link>
  • [-] other?