feat(Youtube Player): view loading status and load programmatically

### Feature Description

Since the ready event is not fired anymore (https://github.com/angular/components/issues/28834), I would like to know if the player has been loaded yet or not (still showing placeholder). Is there already an api for that? If so I did not find it.

Furthermore it would be great if there were a way to programmatically load the player.
(The load method is currently private to the player component.)

"Dirty" workaround:
I am accessing the placeholder via css selectors and dispatching a click event on them in order to trigger the player load.

### Use Case

Example use case: UI Button that will trigger the player to play.
=> The button label may change depending on the loaded status and the click might trigger the player to load and start.

_PS: Thanks for the wrapper component. 🙏_

Youtube Playerコンポーネントと、現在privateになっているそのloadメソッドから始め、コンテキストとしてリンクされたready-event issueを使用します。完了の定義は、Playerがロード済みかどうかを判断するための公開された方法と、プログラムからロードするためのpublicな方法を提供し、説明されているボタンのユースケースをサポートすることです。

索引モデルが issue の本文から書いたものです。