Function parameter is not rendered correctly in CommonMark

[domcorvasce]

Hi.
First, let me say that I really appreciate SwiftDoc and the work you're putting into it. It's awesome.

I noticed a minor issue that arises when listing function parameters in Markdown.
This issue does not concern the HTML documentation.

How to Reproduce

Code:

/// Does something with two-dimensional arrays
///
/// - Parameter arr: Two-dimensional array of elements
init(_ arr: [[ElementType]]) {
  // ...
}

Markdown:

- arr:​ - arr:​ Two-dimensional array of elements

Fix

#171