Following XML elements should be closed: - https://github.com/planetarium/libplanet/blob/main/src/Libplanet.Action/State/World.cs#L34 - https://github.com/planetarium/libplanet/blob/main/src/Libplanet.Action/State/World.cs#L38 - https://github.com/planetarium/libplanet/blob/main/src/Libplanet.Action/State/World.cs#L55
