Update changelog with releases 2.1.20 and 2.2.2–2.2.7

[Copilot]

Changelog was missing six releases after 2.2.1. Adds entries for all missing versions based on commit history.

Added entries

• 2.2.7 — Upgraded Netty to 4.1.132
• 2.2.6 — Fixed WebSocket close_wait bug
• 2.2.4 — Fixed bug where reading a chunked request body via InputStream could throw an exception
• 2.2.3 — Client TLS SNI hostname now accessible via connection.sniHostName()
• 2.2.2 — Upgraded Netty to 4.1.131
• 2.1.20 — Upgraded Netty to 4.1.127 (inserted between 2.1.19 and 2.2.0)

2.2.5 omitted (identical commit to 2.2.6). Versions 2.1.13–2.1.17 omitted (build/deploy infra changes only, no user-facing impact).