Suggest list MouseEvent listener duplicates

[japonicus]

The mouse event handlers added to the 'Powered by MapBox' link at the foot of the suggestions list are added again to _footerNode each time the suggestions are redrawn. This leads to an accumulation of many duplicate 'mousedown' and 'mouseup' handlers.

mapbox-gl-geocoder/lib/index.js

Lines 288 to 303 in 66c236f

	// Add support for footer.
	var parentDraw = typeahead.list.draw;
	var footerNode = this._footerNode = getFooterNode();
	typeahead.list.draw = function() {
	parentDraw.call(this);
	footerNode.addEventListener('mousedown', function() {
	this.selectingListItem = true;
	}.bind(this));
	footerNode.addEventListener('mouseup', function() {
	this.selectingListItem = false;
	}.bind(this));
	this.element.appendChild(footerNode);
	};

The event handlers should be added to _footerNode only once, outside of typeahead.list.draw()

I noticed this because it was apparent that the _footerNode wasn't being garbage collected in a Single Page App that I was debugging.