Soft line breaks

[DeanWay]

Hello 👋

I'm starting this discussion to share my implementation of soft line breaks, and hopefully contribute it to Quill so that others can use this feature out-of-the-box.

For clarity, I use the term "soft line break" to mean a line break that continues the current block formatting.

to use markdown as an example, the first bullet point here includes a soft line break:

• this is
  the first bullet block
• this is the second bullet block

In html a soft break might be implemented using a <br /> tag:

<ul><li>Hello<br />World</li></ul>

rendered as:

• Hello
  World

Proposed Implementation

I've opened a PR here with my proposed implementation: #4565

I opened this PR as a way of focusing this discussion, and offering my work as a starting point for providing a solution on this feature. I think there has been enough of a history of requests on this feature that it makes sense to provide a solution out-of-the-box, but I am also open to implementing something that allows this behaviour to be easily opted into without requiring it.

History of this feature request

It seems there have been a number of issues over time requesting this feature
#252
#4248
#3874
#2469

I have used Quill for a while, but this is my first attempt at a contribution so please let me know if there's something I'm missing!