[MC-54712] floating boats

when making boats ride another, they will fly until somebody interacts with them

command:

summon Boat ~ ~ ~-2 {Invulnerable:1,Riding:{id:Boat,Invulnerable:1,Riding:{id:Boat,Invulnerable:1}}}

summon Boat ~ ~ ~-2 {
    Invulnerable: 1,
    Riding: {
        id: Boat,
        Invulnerable: 1,
        Riding: {
            id: Boat,
            Invulnerable: 1
        }
    }
}