Spec test processSyncAggregate

[twoeths]

Currently lodestar has Block as a param in order to extract signature from there https://github.com/ChainSafe/lodestar/blob/fd1dac853d059ce250d706932daa55e77c33310a/packages/state-transition/src/block/processSyncCommittee.ts#L15

this is not the same to the spec. Need to figure out how the current lodestar implement spec tests for it and do the same thing for state-transition-z

more on that: #17 (comment)