3.6.0

This release of optional lite contains the following changes:

Additions:

• Add non-standard value_or_eval() (#67).
• Add [[nodiscard]] to relational operators.
• Add GitHub Actions CI and badge for it (nonstd-lite-project issue 55).

Changes:

• Update actions/checkout in GitHub Actions to v4 (#78, thanks @striezel).
• Update actions/checkout in GitHub Actions to v3 (#71, thanks @striezel).
• Add/update example/CMakeLists.txt (nonstd-lite-project issue 56).
• Remove gcc 8 and clang 8, 9, 10 from GitHub CI matrix (nonstd-lite-projet issue 69).
• Add common CMake generated files to gitignore (#75, thanks @kacf).
• Remove Travis CI configuration and badge (#73, thanks @striezel).
• Remove msvc (windows-2016) image from GitHub Actions (nonstd-lite-project issue 61, thanks @xavier2k6).
• Add msvc (windows-2022) image to GitHub Actions (nonstd-lite-project issue 62).
• Do not cancel all jobs in a workflow if one fails. (#72, thanks @striezel, nonstd-lite-projet issue 71).
• Use toplevel unit_name (nonstd-lite-project 56).
• Update CMakeLists.txt for examples (nonstd-lite-project 56).
• Change value used with *_CPP20_OR_GREATER to 202002L (nonstd-lite-project issue 49) Now, designate C++23 as speculative.
• Prevent undefined _HAS_EXCEPTIONS warning with Clang (#68, thanks @redbaron).
• Use ternary operator and C++11 constexpr.
• Use optional_constexpr14 with value_or_eval() (#67).
• Accommodate VS2013/MSVC12.0/1800 and earlier.
• Update Readme guided by markdownlint.
• In Readme, update test specification, add folding (#67).
• In Readme, correct URLs for reference [10] Generic: Discriminated Unions.
• In Readme, add Daniela Engert's Boost20.optional to section Other implementations of optional.

Fixes:

• Fix to use forwarding reference (thanks @matthew-wozniczka, fixes #74).
• Fix some typos (#70, thanks @striezel).
• Fix construction, emplace from const types (#69, thanks @atorstling).
• Fix cmake config file to use @package_nspace@ (nonstd-lite issue 68).