Add Nuer language (nus)

Requested at https://translatewiki.net/wiki/Support ,
but I cannot link to the request as it had to be
deleted because of a LiquidThreads bug.

data/langdb.yaml

@@ -433,6 +433,7 @@ languages:
   nr: [Latn, [AF], isiNdebele seSewula]
   nrm: [Latn, [EU], Nouormand]
   nso: [Latn, [AF], Sesotho sa Leboa]
+  nus: [Latn, [AF], Thok Naath]
   nv: [Latn, [AM], Diné bizaad]
   ny: [Latn, [AF], Chi-Chewa]
   nys: [Latn, [PA], Nyungar]