The told pull request is going to be closed now in favor of this new Custom-Dark theme built as a standalone add-on for Mail-in-a-Box.
- Please, test it at your end and post here is any issue arise at your end.
In all cases, your comments about, are very important to make this new Mail-in-a-Box add-on to leave its current BETA level.
Waiting your feedback,
c.c. @JoshData , @jrsupplee