SvelteKit streaming support; parallel step hangs fixed

Minor Changes

• #1376 525a6743 Thanks @gwax! - Add streaming support to inngest/sveltekit serve handlers.

Patch Changes

• #1620 08ef03b9 Thanks @KiKoS0! - Fix run hangs on parallel steps when optimizeParallelism is off

• #1615 9b5ea64c Thanks @Linell! - Fix a crash when using serve({ streaming: true }) and the client disconnects before a run completes

• #1618 922e2024 Thanks @Linell! - Fix step.run and step.invoke output types collapsing to {} for objects with optional properties when using two or more middleware