v3.1.0

Features

• 777cc55 support GraphQL Upload Spec (#175)

Fixes

• e666f69 send headers from .setHeaders to server (#202)
• f13fbb9 remove npm lock file
• 9324747 add missing headers type import / export (#198)
• 8bdb803 remove TS 3.8+ import type syntax (#191)

Improvements

• 2b7ecbd deps: update cross-fetch to latest
• b17fd71 test: add test coverage for headers
• 10c23fa test: refactor test modularity
• 9c36d68 test: refactor upload tests
• 762735b docs: Add example for Mutations to README (#197)