A major new feature release, see release announcement.

• Feature: Add IPv6 support to Connector (implement "Happy Eyeballs" algorithm to support IPv6 probing). IPv6 support is turned on by default, use new happy_eyeballs option in Connector to toggle behavior. (#196, #224 and #225 by @WyriHaximus and @clue)

• Feature: Default to using DNS cache (with max 256 entries) for Connector. (#226 by @clue)

• Add .gitattributes to exclude dev files from exports and some minor code style fixes. (#219 by @reedy and #218 by @mmoreram)

• Improve test suite to fix failing test cases when using new DNS component, significantly improve test performance by awaiting events instead of sleeping, exclude TLS 1.3 test on PHP 7.3, run tests on PHP 7.4 and simplify test matrix. (#208, #209, #210, #217 and #223 by @clue)