Street names in arabic script are missing

[rkversion]

Zoom in to e.g Doha, Qatar or Tehran, Iran and there are no street names visible.
Need to find out at which stage they are being dropped, and fix.

[timwaters]

just a little update image:

Using Noto Sans, merging languages together and creating glyphs and using the mapbox-gl-rtl-text plugin.

However I think the merging process might exclude some CJK (chinese, japanese, korean) characters so some additional steps/checks needed before PR ready.