Add directional arrows to waterway=weir rendered as lines (close #6615)

modules/osm/tags.js

@@ -104,6 +104,9 @@ export var osmRightSideIsInsideTags = {
     },
     'man_made': {
         'embankment': true
+    },
+    'waterway': {
+        'weir': true
     }
 };
 

modules/svg/defs.js

@@ -58,6 +58,7 @@ export function svgDefs(context) {
         // the water side, so let's color them blue (with a gap) to
         // give a stronger indication
         addSidedMarker('coastline', '#77dede', 1);
+        addSidedMarker('waterway', '#77dede', 1);
         // barriers have a dashed line, and separating the triangle
         // from the line visually suits that
         addSidedMarker('barrier', '#ddd', 1);