#135 feat: add broadcasts->cancel() method

Summary

• Adds Broadcast::cancel($id), calling POST /broadcasts/:id/cancel via the shared Payload::cancel() helper (already used by Email::cancel()).

Part of the broadcast cancel rollout: resend/resend-monorepo#8126, resend/resend-openapi#85, resend/resend-node#1059, resend/resend-docs#1722, resend/resend-go#144, resend/resend-java#122.

Test plan

• vendor/bin/pest — 183/183 passing, including the new can cancel a broadcast resource case
• php -l on touched files — clean

🤖 Generated with Claude Code

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Summary by cubic

Add support to cancel a queued or scheduled broadcast via Broadcast::cancel($id) (POST /broadcasts/:id/cancel), mirroring Email::cancel(). Bumps SDK version to 1.8.0.

• New Features

  • Added Broadcast::cancel($id) using the shared Payload::cancel() helper; returns a Broadcast resource.
  • Added test and PHPDoc for Broadcast::cancel().

• Dependencies

  • Bumped SDK version to 1.8.0.