add height parameter to map component (#829)

This parameter is used in the example below

Author: setop

examples/official-site/sqlpage/migrations/10_map.sql

@@ -85,6 +85,14 @@ VALUES
         TRUE,
         TRUE
     ),
+    (
+        'map',
+        'height',
+        'Height of the map, in pixels. Default to 350px',
+        'INTEGER',
+        TRUE,
+        TRUE
+    ),
     (
         'map',
         'latitude',
@@ -246,4 +254,4 @@ or abstract 2D data visualizations.
             }
             ]'
         )
-    );
+    );