Remove or modify the use of the Marker API

[riastrad]

By default, L.mapbox.style.marker points to a deprecated Mapbox API (v4/marker):

mapbox.js/src/marker.js

Lines 23 to 26 in 3ac9871

	iconUrl: format_url('/v4/marker/' +
	'pin-' + size.charAt(0) + symbol + '+' + color +
	// detect and use retina markers, which are x2 resolution
	(L.Browser.retina ? '@2x' : '') + '.png', options && options.accessToken),

This integration needs to either be updated to retrieve some other default marker or be removed entirely.

[riastrad]

It's probably possible to avoid endpoint I/O entirely and use @mapbox/makiwich to generate these endpoints on the fly client-side. I think this would be preferable to removing the marker API from Mapbox.js.

[riastrad]

Investigating today - it looks like incorporating @mapbox/makiwich as a dependency would break some of our browser backward compatibility because of it's use of template literals.

Another solution might be to migrate the current use of the /marker/ endpoint to a similar request to the modern Static Images.

[riastrad]

This one is looking to be a little hairier than anticipated, so I'm de-scoping it from the current push for a new minor release.