Proof of concept of a Rich Content Editor using TipTap

This proof of concept attempts to make some of the concepts and design decisions described in the WYSIWYG editor architecture issue concrete by demonstrating them in an example. It sets up TipTap, ProseMirror, and Markdown-it to implement a WYSIWYG editor that generates Markdown from rich text and convert markdown to a rich text. You can see the raw markdown in the "Source view" and the rich text version in the "Editor view". Changes between the two modes are synchronized.

Markdown view	Source view

This Merge Request is heavily annotated to indicate how each concept in the architecture documentation translates to its source code. The editor implemented in this MR supports a small subset of the Commonmark specification. It also includes a frontmatter plugin to showcase the extensibility and modularity characteristics of the architecture.