trailing-whitespace: default --no-markdown-linebreak-ext?

[asottile]

markdown files allow using trailing whitespace to signify a line break

• I've fielded quite a few questions that are "trailing-whitespace is broken, it doesn't work on markdown files".
• I've never seen someone intentionally use this feature

I'm proposing disabling the "skip markdown trailing whitespace" by default and allowing one to opt in to the behaviour.

Thoughts?