The key at the specified index or null if
beyond the storage capacity. A rejected promise represents an API
violation.
Example
// To get a key at an index. Either string or null if not found // Defaults to STORAGE_TYPE.Local letkey = awaitstorage_key({index:0}); // To specify type letkey = awaitstorage_key({type:STORAGE_TYPE.Session, index:0});
Retrieves the key at the specified index.