WebSocket 1.0.0

Introducing WebSocket 1.0 🎉
🔌 Non-blocking, event-driven WebSocket client and server built on Swift NIO.

Docs:
https://docs.vapor.codes/3.0/websocket/getting-started/

API Docs:
https://api.vapor.codes/websocket/latest/WebSocket/

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This module has been moved from the old vapor/engine repo to its own package. This will make it easier to version going forward 🙌.

Milestone:
1.0.0