Style linking names for instances

[colinmford]

Hi @LettError —

In the DS5 spec there are additional names available other than what is shown in the instances tab.

https://fonttools.readthedocs.io/en/latest/designspaceLib/xml.html#instances-element

Most important of those, I think, are the stylemapfamilyname and stylemapstylename elements. These are quite useful for getting style linking to work in static fonts generated from the instances in a Designspace document. If they are left unset, the build tool just makes a best guess as to what NID 1 and 2 in the name table should be, and it could be wrong. I always find myself adding these names in the XML afterwards, which is fine for me but might be confusing for others.

It would be nice to have these names on the instance tab. If not in the table (I know it is quite crowded there and clutter should be kept to a minimum), maybe it could be the first tab on the "info" popup (which currently contains settings for localized names).

If this sounds like an idea you would like to see, I can make a PR to that effect.