Rton to JSON can fail for unicode.

[Haruma-VN]

Hi, here is the rton https://drive.google.com/file/d/15mdyEVIVi49_cuEXfYAC7VbMNcKRgvpd/view?usp=sharing

[nineteendo]

https://drive.google.com/uc?id=15mdyEVIVi49_cuEXfYAC7VbMNcKRgvpd

[nineteendo]

Here's the error log: fail.txt It's caused by the convertor using the byte size of utf-8 text instead of the character length. In order to fix it whilst keeping the tool fast, I need to write a C library.