Add getAllPlaylistItemsByPlaylistId() method

[ghost]

Will probably need changing to meet code style of library

Could do with metadata added to returned array

As such, unsure how a test would look like

[guoxiangke]

great job! I need this function!

[guoxiangke]

refactor by GPT

function getAllPlaylistItemsByPlaylistId($playlistId) {
    $playlistItems = [];

    $params = [
        'playlistId' => $playlistId,
        'part' => 'id, snippet, contentDetails, status',
    ];

    do {
        $raw = Youtube::getPlaylistItemsByPlaylistIdAdvanced($params, true);

        if ($raw['results'] !== false) {
            $playlistItems = array_merge($playlistItems, $raw['results']);
        }

        $params['pageToken'] = $raw['info']['nextPageToken'] ?? null;
    } while ($params['pageToken'] !== null);

    return $playlistItems;
}