Major version bump from 11.0.3 to 16.0. The legacy API
(websockets.legacy.*) was removed in 14.0; the current public
API (connect/serve in websockets.asyncio.*) is stable and
backward-compatible since 12.0. Add test.sh that verifies core
imports (frames, http11, datastructures).
Changelog: https://websockets.readthedocs.io/en/stable/changelog.html
Signed-off-by: Alexandru Ardelean <alex@shruggie.ro>
