fix: handle truncation better when text is multiline

[matslindh]

This fixes an issue where the newline would be considered part of the last word to be truncated,
effectively removing the last word on the line, even if the word by itself up to the newline
could fit properly.

Example:
foo bar
baz

This would receive "foo", "bar\nbaz" as truncation targets, and "bar\nbaz" would be stripped out.

This patch handles newlines explicitly, trying to keep as many lines in the last token as possible.
To avoid getting "bar..." as the continuation, a space is added before the ellipsis if truncation
happens on the end of the line. This way we avoid implying that "bar" is the word that has been
truncated, but instead that the message continues further down.

This might not work as expected with other forms of continuation texts, but in any case the patch
should behave better than the previous version.