Programmatic way to allow a JavaScript client to render tiles

[ahmadayubi]

Link emits 'tile' events which have x, y, zoom and a callback in details that allows the user to append to the tile on the map at a given coordinate.

For example:

let tileEventSource = document.querySelector("body > mapml-viewer > layer- > extent > link");
tileEventSource.addEventListener("tile", (e) => {
    let cusTile = document.createElement("IFRAME");
    cusTile .src = "https://www.youtube.com/embed/yI2oS2hoL0k?autoplay=1&mute=1";
    cusTile .width = 256;
    cusTile .height = 256;
    e.detail.appendTile(cusTile );
});

There's a full example in debug/clientTile.html

Closes #219