1.6.2

• Added approx.hpp and compare.hpp, which allow users to compare C++ struct that have a glz::meta without needing to define a spaceship operator. Even more useful is glz::approx_equal_to, which allows users to define a single compare_epsilon in the glz::meta and compare structures with floating point types against that epsilon.
• Lots of internal code cleanup, simplification, and dead code removal