add option to force insert line breaks to highlighting code.

[dindinw]

Add a option which allow force insert <br> into the <pre> of the syntax highlighting code in the case when CSS "write-space:pre" not work. The option is off by default.

enable the option, let the line breaks work in the case.

[liudongmiao]

+1

@adam-p And if you want to merge this, I'll add a Chinese translation for this patch.

[concefly]

I really think so. +1

[adam-p]

In what scenario does "write-space:pre" not work? I don't mind adding this, but I need to know why.

[dindinw]

@adam-p originally, the issue I had faced when I tried to use wechat's editor(https://mp.weixin.qq.com/) to publish my articles, which failed to handle the line-breaks of the syntax highlighted code lines. I can't remember the details and reason why"write-space:pre"not work in the case after a long period of time, Sorry for my bad memory. Anyway, force to replace '\n' to <br> fix the issue. hope this helps -Alex

[lonnyzhang423]

+1