yaml frontmatter not handled correctly

I've noticed that my markdown files with yaml frontmatter show up in the preview pane with the formatting all messed up.
- disregards carriage returns
- treats last line before frontmatter end markdown string "---" as a title

While working on this, suggest to also consider what is the desired behavior for frontmatter. In the example below, VS Code hides yaml-formatted frontmatter, and I believe that is the most common default behavior. Displaying frontmatter is also a valid choice IMO but ofc it should be an intentional design decision.

Example images below.

**VS Code (correct formatting applied):**

**MacDown (incorrect formatting):**

example images.

Start by reproducing the issue in the MacDown preview pane with a Markdown file containing YAML frontmatter, including carriage returns and a final line of "---". Trace the preview rendering or Markdown parsing entry point mentioned by the behavior, then define whether frontmatter is hidden or displayed and verify that line breaks and delimiters render correctly.

Written by the indexing model from the issue text.