Hey,
I think this has been slightly discussed before, but I’m not sure if this specifically. I’ve tried to check if there is any solution around, but there isn’t.
It would be great if the “ignored words” for the spell checker could be added in a dedicated file instead of the just a section in the settings.
I use ST3 a lot for writing and I guess that this list is going to get pretty big at some point, which I guess it’s going to become annoying to have it on the settings file. Even more at the beginning of the file.
So, I think a dedicated file for this matter would be much handier.
As a bonus track, it would be great to be able to have a multi-language dictionary, or spell more than one language at the same time. 
.