v6.0.0-rc.7

What's Changed

• refactor(dns): make hickory module internal by @0x676e67 in #881
• fix(request): correct default_headers method semantics by @0x676e67 in #882
• feat(ws): option for default_headers method in websocket by @0x676e67 in #883

Full Changelog: v6.0.0-rc.5...v6.0.0-rc.7