Filter out duplicate features with the largest one

[tristen]

It looks like multiple accessible markers are being added when features span more than one tile

From the docs on queryrenderedfeatures:

Because features come from tiled vector data or GeoJSON data that is converted to tiles internally, feature geometries may be split or duplicated across tile boundaries and, as a result, features may appear multiple times in query results.

Its extra work from the plugin but I wonder if it should filter out duplicates and then find the largest result so the width and height of the button is accurate. cc @andrewharvey