Wrong CriticMarkup output when used to gfm option

[IpShot]

Issue happened when try to get diff result in CriticMarkup and pass to: gfm option.

• Insert output looks fine: {++Hey++}

• Delete output: {–Hey–} ('–' instead of '--')

• Substitution output: {\\\\~<sub>protect access,</sub>\\\\>protect,\\\\~\\\\~}

• It also adds \n characters on the same places in md text despite of wrap: preserver/none or columns options. Seems like it just ignores them while using to: gfm

• Wrong result with CriticMarkup errors variations also happened when tried to: commonmark, to: markdown.