Translation failures using italics within a word

[bjones1]

When the CodeChat Editor Client is used to add italics with a word (instead of including the entire word), the resulting Markdown is incorrect. For example, changing "August 1994" to "August 1994" instead produces "\_Aug_ust 1994". This is an issue using the Turndown library -- see mixmark-io/turndown#441. To fix this, merge this PR into the Turndown fork used by the CodeChat Editor at https://github.com/bjones1/Turndown, then retest/rebundle.

[bjones1]

Fixed (along with a few other Turndown bugs) in bjones1/turndown@178b4c1 and 19f4bc5.