fix(sc): support emitting Maps in ScriptBuilder

[ixje]

close #909

• [x] validate emitPush on a map works as intended and is not consumed by https://github.com/CityOfZion/neon-js/blob/master/packages/neon-core/src/sc/ScriptBuilder.ts#L91-L92

[ixje]

closed in favour of same PR from own repo because otherwise CI won't trigger