Add name_de to documentation

layers/transportation_name/transportation_name.yaml

@@ -9,7 +9,8 @@ layer:
   srs: +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0.0 +k=1.0 +units=m +nadgrids=@null +wktext +no_defs +over
   fields:
     name: The OSM [`name`](http://wiki.openstreetmap.org/wiki/Highways#Names_and_references) value of the highway.
-    name_en: The english `name:en` value if available.
+    name_en: English name `name:en` if available, otherwise `name`.
+    name_de: German name `name:de` if available, otherwise `name` or `name:en`.
     ref: The OSM [`ref`](http://wiki.openstreetmap.org/wiki/Key:ref) tag of the motorway or its network.
     ref_length: Length of the `ref` field. Useful for having a shield icon as background for labeling motorways.
     network: