Provide default contents for Marker

[jfirebaugh]

For closer parity with Leaflet markers, the element parameter to the Marker class should be optional, and the default should be render a traditional marker pin icon similar to .

For implementation, I suggest that this use some inline SVG source, so as not to require an external asset.

[mikehatfield]

Any progress on this?

[jfirebaugh]

@mikehatfield Nope -- want to work on a PR?

[rahuldhawani]

Anyone working on this? If not, then I would like to pick it up.

[jfirebaugh]

Go for it @rahuldhawani!

[samanpwbb]

I recommend this marker, for consistency across gl native / mapbox's static image API: https://github.com/mapbox/makiwich/blob/master/sources/marker-large.svg

[Qwertie-]

This would be very helpful. It's overly complex to add a basic marker to the map currently.