Add Fira GO

https://github.com/bBoxType/FiraGO

> In 2016, the geo data provider Here chose Fira Sans as their corporate typeface. Their need for a broader language coverage especially in map applications led them to commission us with a global script extension. Thanks to our great team of designers, consultants and technicians, the project was completed by 2017.
>
> Based on the Fira Sans 4.3 glyph set, FiraGO now supports Arabic, Devanagari, Georgian, Hebrew and Thai. With this script support, FiraGO catches up with other globally extended and free typefaces such as Noto.
>
> We decided to introduce FiraGO as a new product. That way, users of Fira Sans can also install FiraGO. For further information please have a look at the Fira site.
>
> https://bboxtype.com/typefaces/FiraGO

Note this has a HUGE range of weights (https://github.com/bBoxType/FiraGO/tree/master/Fonts/FiraGO_TTF_1001/Roman) and will either need commissioned work to upgrade to a VF weight axis, or special packaging into sibling families.