Broaden receive data buffer types

[Mirochill]

Summary

• widen Connection.receive_data() and the internal receive buffer annotations to accept bytearray and memoryview alongside bytes
• add a regression test covering both supported bytes-like inputs
• document the backward-compatible API expansion in the news fragment

Why

Issue #186 points out that receive_data() already operates on bytes-like input, but its public annotation is still narrower than the runtime behavior. Widening the concrete accepted types removes false positives for downstream users adopting stricter bytes checking while keeping this patch intentionally small for h11's current typing/tooling baseline.

Validation

• No local validation run, per this workspace's coordination-only policy.
• Performed static review of the receive path and confirmed Connection.receive_data() forwards directly into ReceiveBuffer.__iadd__().
• Verified the patch shape with git diff --check.
• Relying on the repository's remote CI for execution feedback.

Fixes #186.