Remove Globals - Support ShadowDom for modern browsers and ShadyDOM polyfill for IE

[panthershark]

Overview

I'm wrapping quill with a webcomponent so it can be used with common diff/patch libraries (we are using Elm, but this should be possible with any diff/patch implementation). In order to make things work correctly with ShadowDOM, all of the global stuff needs to be refactored. This is what I attempted to do here.

Changes

• Remove all assumptions that there is only 1 document and that document is global.
• Separate the assumption that document is the only thing that implements getSelection() see MDN docs
• Initialize with sensible defaults that do not change the current global assumptions
• Refactor the global listeners so they avoid using the DOM to store the quill instance node.__quill it assumes things that break ShadowDOM and the separation which is intended.

How do we ge this published?

I'm not sure how to trigger all of the build/test stuff in this library or what processes y'all use to get a release published. If there is anything I can do to help with getting this published, please LMK.

[panthershark]

For the case where someone uses this globally in plainJS, the destroy function needs to be called.

• Update docs to require users to call destroy
• Setup some kind of detach listener which calls destroy

This is probably worth a conversation.

[panthershark]

With the new optional parameters, this is what the initialization in a webcomponent looks like (with simplification b/c of the HTMLElement lifecycle)

class QuillEditor extends HTMLElement {
  constructor() {
    super();
    const root = this.attachShadow({ mode: 'open' });
    root.innerHTML = `<div id="editor"></div>`;

    const editor=  root.getElementById('#editor');
    const quill = new Quill(editor, {
      modules: { .. },
      theme:  'snow',
      document: root.ownerDocument,
      selectionRoot: root
    });
  }
}

[panthershark]

selectionRoot can be a Document or ShadowRoot. If a Document is passed when using a webcomponent, then it will never select any of the nodes inside ShadowDOM and all of the selection/intersection validation inside of Quill breaks.

[panthershark]

The above function should provide a reasonable fallback for use cases where

• it is assumed that there is one document
• ShadyDOM is polyfilled in IE