cfug/dio http2_adapter_v2.9.0 on GitHub

What's new

Expose supportedProtocols on ConnectionManager (defaults to ['h2'],
fully backwards-compatible). Setting it to ['h2', 'http/1.1'] fixes
fallbackAdapter silently never firing against RFC 7301-compliant servers
that abort the TLS handshake with no_application_protocol when only h2
is advertised.
Fix socket leak: when DioH2NotSupportedException is thrown after a
successful TLS handshake (server selected http/1.1 instead of h2),
the SecureSocket is now explicitly destroyed before routing to
fallbackAdapter, rather than being abandoned.
Deprecate the misspelled ConnectionManager.handshakeTimout parameter in
favor of the correctly spelled handshakeTimeout; the deprecated alias
keeps working and is scheduled for removal in 3.0.0.