Unmatched backticks on a single line should be output as is

[s-ludwig]

Instead of rendering the rest of the line as inline code, single backtick characters should just be output as-is, as implied by the spec.

[CyberShadow]

For dlang.org we would probably prefer maximum strictness, though; a $(BACKTICK) isn't that much of an issue in cases where it's needed. I guess that could be done by a separate tool, like DScanner.