fkYAML version 0.3.12

* updated ryml & fix usage in benchmark app

* skip include libfyaml header on windows

* modified build configs

* replaced benchmark input data files & updated README for benchmark

* updated benchmark section in README.md

* updated REUSE template file for library source files

* updated header lines of library source files

* improved lexical analysis state management

* added comments

#401)

* fixed compile warnings/errors when building benchmarker app with msvc compilers

* ignore C4819 warning when compiling rapidyaml with msvc

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* Fix some typos in strings and comments

* Replace all _HPP_ defines with _HPP

This commit fixes CppInconsistentNaming issue

* Rename TO_STRING_HPP define

* Fix another typos

* move scalar node creation from deserializer to scalar_parser

* separate unescaping for single quoted scalars from lexical analysis

* create a function exclusively for plain scalar range detection (outside flow context)

* added state of whether owned buffer is used in scalar_parser

* merged scanning plain scalars when inside/outside flow contexts in lexer

* separate parsing of double quoted scalar from lexer's scanning

* added runtime assertions & cleaned up unused codes

* made basic_str_view ctors constexpr if applicable

* separate block scalar parsing from lexer's scanning

* removed owned buffer in lexer

* wip: adding tests for scalar_parser class

* separate node creation depending on lexical token type

* reduced unnecessary branching in lexer's scanning of scalars

* added test cases for scalar_parser

* added missing function header comments

* updated benchmarking scores

* fixed warnings and errors

* fixed wrong parse result from single scalar document

* clean up unused codes