poster prop is not declarative (does not update poster when URL changes)

Hello Cloudflare team,

We have a use case where we are using an external 'video picker' list to select a video they want to watch.

Once they click it, we update the props going to the `` component, including the `src` and `poster` props.

The `src` prop seems to take effect, because starting the video does in fact play the selected video, however the poster does not change.

It looks like it's an intended behavior due to the `useMemo` implementation without dependencies here:
https://github.com/cloudflare/stream-react/blob/fda143fde6e235706ae14afc9dc919a11374c15b/src/useIframeSrc.tsx#L53-L59

Which says you can use the SDK to make the changes... but I don't see how.

Thanks in advance - we're hoping to switch to Stream from a competitor but this is blocking our implementation :)

まず src/useIframeSrc.tsx の53-59行付近を読み、特に issue で説明されている useMemo の動作を確認します。src と併せて Stream コンポーネントの poster prop を変更してケースを再現し、URL が変わったときに表示される poster が更新されることを確認します。

索引モデルが issue の本文から書いたものです。