- add documentation for win fct helper
- add new macro YYCC_U8_CHAR for casting ordinary char to yycc utf8 char.
- add documentation for new added YYCC_U8_CHAR.
- rename Constrain to Constraint in code and documentation.
- remove massive annotation of encoding helper because the documentation is enough.
- fix doxygen character shift warnings.
- add a new split function, SplitView which can reduce cost memory by using string view.
- add a new testbench for split function for testing empty source string.
- add documentation for some string helper function.
- improve library encoding documentation.
- add Doxygen build configuration file template and CMake list file.
- add option for building documentation.
- the content of documentation should be filled in future.
