StyleImageMissing

A style needs an image that is missing from the sprite sheet. This event is emitted when the `map` renders visible tiles, and one of the required images is missing in the sprite sheet. The event observer has to provide the missing image by calling the `addStyleImage` method. Note: Images added as a result of the `StyleImageMissing` event will be treated as user-added images, and when the engine no longer needs a user-provided image, the `map` will emit `StyleImageRemoveUnused` event.