Find images links in the editor

Hi @hemanthmc 
I can suggest subscribing to `sorter:drag:end` event and pass a React method as a callback.
In the method check if image is dropped and store its src into React state or do whatever needed. 

A more detailed example:
`this.grapesjsInstance.on('sorter:drag:end', this.onDragEnd);`

`onDragEnd(DataTransfer, modelToDrop) {
        if (modelToDrop && modelToDrop.attributes && modelToDrop.attributes.type === 'image') {
            this.setState({ /* data to save */ });
        }
    }`