Add waterway=drain

Author: pnorman

shortbread-website/content/schema/1.1.md

@@ -87,12 +87,13 @@ Holds waterway line geometries. Features are sorted by their {{< tag layer >}} t
 
 #### Features
 
-| Type of feature | Value of `kind`   | OSM tag                     | Geometry | Zoom                                                                          |
-| --------------- | :---------------- | :-------------------------- | :------- | :---------------------------------------------------------------------------- |
-| Canals          | `canal`           | {{< tag waterway canal >}}  | line     | Canals are available if their line is longer than 0.25 pixel but not below 9. |
-| Rivers          | `river`           | {{< tag waterway river >}}  | line     | Rivers are available if their line is longer than 0.25 pixel but not below 9. |
-| Streams         | `stream`          | {{< tag waterway stream >}} | line     | 14+                                                                           |
-| Ditches          | `ditch`           | {{< tag waterway ditch >}}  | line     | 14+                                                                           |
+| Type of feature    | Value of `kind`   | OSM tag                     | Geometry | Zoom                                                                          |
+| ------------------ | :---------------- | :-------------------------- | :------- | :---------------------------------------------------------------------------- |
+| Canals             | `canal`           | {{< tag waterway canal >}}  | line     | Canals are available if their line is longer than 0.25 pixel but not below 9. |
+| Rivers             | `river`           | {{< tag waterway river >}}  | line     | Rivers are available if their line is longer than 0.25 pixel but not below 9. |
+| Streams            | `stream`          | {{< tag waterway stream >}} | line     | 14+                                                                           |
+| Drainage waterways | `drain`           | {{< tag waterway drain >}}  | line     | 14+                                                                           |
+| Ditches            | `ditch`           | {{< tag waterway ditch >}}  | line     | 14+                                                                           |
 
 ### Layer "water_lines_labels"