Changes

• Fixed a typo in README
• Added /utf-8 when building modules with MSVC, similar to fmt
• Relaced std::construct_at(this, ...) and std::destroy_at(this) in proxy with private function calls. Otherwise, UB is inevitable (like reset()), although it passes unit tests.
• Removed null initialization form details::invocation_meta and meta_ptr_indirect_impl as they are no longer required.