Allow word wrap in git diff middle panel.

[RokeJulianLockhart]

It's frustrating to view otherwise:

It would probably also be important for #684 (comment).

[Murmele]

As workaround you can collapse the left panel by the button above and by pressing CTRL + M you hide wether the Commit List or the diff view (https://murmele.github.io/Gittyup/)

[RokeJulianLockhart]

#706 (comment)

@Murmele, thanks, but my lines are too long (I work on Markdown documents with only paragraph-delimiting line breaks, rather than Python-like mid-line line-breaks) for the additional space that affords to be of use.