Add Workflow Types to workers-types

[AbhiPrasad]

ref getsentry/sentry-javascript#16704

The following types:

WorkflowEntrypoint,
WorkflowEvent,
WorkflowSleepDuration,
WorkflowStep,
WorkflowStepConfig,
WorkflowStepEvent,
WorkflowTimeoutDuration,

are not available via @cloudflare/workers-types (tested with 4.20250620.0). The Sentry Cloudflare SDK needs them for our upcoming Cloudflare Workflows instrumentation. It would be great if they got exposed!

The Sentry SDK ended up vendoring them in, but this will cause problems as the types get updated.