v2.2.1

• Deploy cross-chain contracts on Sepolia testnet & Polygon Amoy testnet. (#23, #24)
• Add whitelist. (#19, #20, #21, #22)
• Add iExec internal network. (#16, #17, #18)
• Migrate to Drone CI. (#13, #14, #15)
• Add prettier. (#11, #12)
• Generate test chain. (#10)