bpo-39128: Added algorithm description (GH-18624) GH- [bpo-39128](https://bugs.python.org/issue39128): happy eyeballs description GH- [3.9] 39128 - happy eyeballs description (GH-18624) GH- [3.8] 39128 - happy eyeballs description (GH-18624) https://bugs.python.org/issue39128 (cherry picked from commit 8af4712a16e4b7d1b60f1faec13cd7a88da95f6a) Co-authored-by: idomic <michael.ido@gmail.com>