v6.0.0-rc.15

What's Changed

• feat(retry): introduce configurable retry policy by @0x676e67 in #935
• test(client): update header tests and examples by @0x676e67 in #939
• chore(sync): remove unused code by @0x676e67 in #940
• refactor(keylog): redesign API for better ergonomics and functionality by @0x676e67 in #941
• refactor(ext): introduce ergonomic and functional API by @0x676e67 in #942
• feat(http1): remove preserve_header_case support by @0x676e67 in #943

Full Changelog: v6.0.0-rc.14...v6.0.0-rc.15