Paragraph continuation broken in lists

[turbo]

Paragraph rules (no new paragraph until repeated horizontal or vertical whitespace) are not processed correctly in lists.

An example:

import markdown

let md = """
Normal paragraph

* bullet item one

* bullet starts here
 and continues here
and this is also the bullet, not a new paragraph

This is a new paragraph though
"""

echo markdown(md, config = initGfmConfig())

Produces:

<p>Normal paragraph</p>
<ul>
<li>
<p>bullet item one</p>
</li>
<li>
<p>bullet starts here
and continues here</p>
</li>
</ul>
<p>and this is also the bullet, not a new paragraph</p>
<p>This is a new paragraph though</p>

Where the second to last paragraph lives outside the list. However, this is what GFM renders:

---

Normal paragraph

• bullet item one

• bullet starts here
  and continues here
  and this is also the bullet, not a new paragraph

This is a new paragraph though

[turbo]

There's an off-by-one error here:

nim-markdown/src/markdown.nim

Line 751 in e6379e2

size = firstLineSize

Adding a +1 seems to superficially fix the bug (all test pass) but that's hacky. I can't quite trace where the offset is coming from.