MD038: Improved fixing for words stuck to backtick

[nschonni]

Currently the fix for MD038 correctly trims the interior of the spans, but sometimes that interior space is because of a missing space after the backtick. EX:

My `code `should be good

Gets fixed to:

My `code`should be good

But ideally it would detect a non-whitespace character trailing the lead/closing backtick and add the padding like:

My `code` should be good