docs: update README for v2.0 with migration guide

- Update install and peer dependency sections for Prisma 7+
- Update all code examples with required prisma option and third type param
- Add options table documenting all queue configuration
- Document events, retry strategy, cooperative cancellation
- Add non-transactional mode section with requeueStale usage
- Add migration guide from v1.x to v2.0 with all breaking changes