Quill 2.0: Support for multiple line-breaks within a single paragraph

[dstj]

This is a modified revival of #2872 as it was closed when Quill 2.0 was released. Also related: #2469

Quote from #2872

Lines and paragraphs are not same things in typography. Usually, there's a spacing between paragraphs, which less than the height of a full line, unless there are different elements involved like figures, headings,... And, sometimes, there's a need to use multiple simple line-breaks for the same paragraph.

There can be produced output allowing multiple line-breaks within a single paragraph, like:

<p>Some text paragraph</p>
<p>
  Another text paragraph:<br/>
  with<br/>
  multiple<br/>
  lines
<p>
<p>Another paragraph</p>

Actual behavior:

Can't produce output above.

Suggested behaviour

In text editors like Microsoft Word (or CKEditor5 and TinyMCE), Shift-Enter will create a simple line break, while Enter will create a new paragraph.

#4248 tried with a custom keyboard binding, but it doesn't work because the underlying Parchment data model that does not support it.

Version
Quill 2.0.2
via ngx-quill: "^25.3.2"