Single newlines in tags get rendered as-is in Discord #3172

According to the markdown spec, lines separated by a single newline should be joined with a space.

Discord embeds doesn't seem to respect this, as demonstrated by the !traceback tag:

We could resolve this by formatting paragraphs on a single line, but I think joining the lines manually as the tag is loaded is better (something along the lines of re.sub(r"(?<!\n)\n(?!\n)", " ", content)) since it leaves open more formatting options.