[Bug] Doc comment's <code> block is not correctly rendered when another tags exists before <code> tag

[filzrev]

Describe the bug

When <para></para> tag exists before <code> tag,
Rendered HTML results is corrupted.

Example documentation comment

/// <remarks>
/// <para>
/// Dummy paragraph.
/// </para>
/// <code lang="cs">
/// public sealed class Sample
/// {
///     public int AAA {get;set;}
///
///     public int BBB {get;set;}
///
///     public int CCC {get;set;}
/// }
/// </code>
/// </remarks>
public class Sample
{
    public int Dummy { get; set; }
}

Rendered Image

To Reproduce

1. Set documentation comment described above.
2. Run docfx metadata command
3. Run docfx build --serve command
4. Confirm API page for Sample class

Expected behavior
<code></code> blocks are rendered as expected.

Additional context
To resolve this issue.
It need to add extra new line before <pre> tag.
That is required when embedding HTML tags on markdown text.

See https://github.com/xoofx/markdig/issues/472#issuecomment-683787240 for details