Marker with img tag looses its focus when it starts dragging.

[cs09g]

mapbox-gl-js version:
v0.52.0

browser:
Firefox 64.0.2
IE 11

Steps to Trigger Behavior

1. create marker with img element
2. set draggable true and add to map
3. start dragging

Link to Demonstration

https://jsfiddle.net/9ru0z3dw/

Expected Behavior

marker should be dragging as expected.

Actual Behavior

marker shows its ghost icon and cursor turns to not-allowed.

Workaround

Setting following code on marker element, it works as expected but, I think this should be a part of library.
element.ondragstart = () => { return false; }

[cs09g]

@mourner May I add that workaround code in marker.js with PR? It'll be placed https://github.com/mapbox/mapbox-gl-js/blob/master/src/ui/marker.js#L184

[ryanhamley]

@cs09g We always welcome PRs! You're right that it would be added in the constructor.