Internal space line is trimmed in converted plaintext

[Goooler]

Convert markdown to plaintext using:

private fun convertMarkdownToPlaintext(markdown: String): String {
    val parser = Parser.builder().build()
    val document = parser.parse(markdown)
    val renderer = TextContentRenderer.builder().build()
    return renderer.render(document)
}

Example:

this
is 

**note**

Expected plaintext:

this
is

note

Actual plaintext:

this
is
note

(Also see what the reference implementation does: https://spec.commonmark.org/dingus/)

[boyshell]

您好！邮件已收到。

[robinst]

The plain text renderer is not really well-defined. But this is something we might change (CC @JinneeJ). Out of interest, what are you using it for?

[Goooler]

I use this to convert markdown from a rich text editor on Android.

[robinst]

Ah this came up in #264 as well. Happy to accept a patch for this as an option on TextContentRenderer.Builder.

[robinst]

Closing as a duplicate of #264