Cleans up all registered message event listeners previously added by _listenForMessage.
Call this method when the instance is being destroyed or no longer needs to listen to messages.
Returns void
init
init():Promise<boolean>
Initializes the LoadManager by listening for a "loadState" message from the iframe.
Resolves when the iframe reports that it's in a "ready" state.
Manages the loading state of an iframe and communicates with it via postMessage.