Custom html marker refer https://docs.eegeo.com/eegeo.js/v0.1.780/docs/leaflet/L.DivIcon/
interface IDivIconInterface {
/**
* A custom class name to assign to the icon.
*/
className: string,
/**
* A custom HTML code to put inside the div element.
*/
html: string,
/**
* Size of the icon in pixels. Can be also set through CSS.
*/
iconSize?: [number, number],
/**
* The coordinates of the "tip" of the icon (relative to its top left corner).
* The icon will be aligned so that this point is at the marker's geographical location.
* Centered by default if size is specified, also can be set in CSS with negative margins.
*/
iconAnchor?: [number, number]
/**
* The coordinates of the point from which popups will "open", relative to the icon anchor.
*/
popupAnchor?: [number, number]
}