Some transformers that render the music-os track schema format `erc721.createdAt` (the block number) as a string when it must be an integer

[TimDaub]

• https://github.com/neume-network/schema/blob/39a4bdb680062599bcd741679515093870798e5d/src/schema.mjs#L226
• @reimertz informed me that for some tracks in music-os-accumulator, we're still formatting createdAt as a string and not an integer