fix: include flynt in darkerconfig

[okuuva]

Included flynt in DarkerConfig options.

Also sorted config options alphabetically.

Fixes #745.

[akaihola]

Thanks @okuuva! Strange indeed that this surfaces only now even though you've previously used the flynt = configuration option successfully.

If you have time, could you add a change log note about this fix? Also, could you check whether this is covered by unit tests?

No prob if you can't afford the time, I'll come back to this myself too.

[okuuva]

If you have time, could you add a change log note about this fix? Also, could you check whether this is covered by unit tests?

No prob if you can't afford the time, I'll come back to this myself too.

Sure, I'll try to get around it later this week.