v0.17.0

Just in time for the holidays, we are happy to announce the release of v0.17.0! 🎄🎉
This release includes a number of compatibility improvements and some project
structure improvements to lay the groundwork for upcoming developments.

• Feature: Improve PHP 8.4+ support by avoiding implicitly nullable types.
  (#266 and #267 by @clue)

• Feature / BC break: Update to require Promise v3.
  (#265 by @clue)

• Feature: Consistent parsing for HTTP CONNECT request method (PHP SAPI).
  (#255 by @clue)

• Minor documentation improvements and update Dockerfile syntax.
  (#261, #268 and #269 by @clue)

• Improve test suite and project structure by cleaning up tests and docs.
  (#256, #267, #270 and #271 by @clue)