Multilingualization of messages

[mtshiba]

I am planning to multilingualize error messages (currently only English, Japanese, Simplified Chinese and Traditional Chinese are supported).

This will be documented so that people who are not familiar with Rust can participate.

Is there anyone who would like to help?

[C-BJ]

I can help translate Simplified Chinese and Traditional Chinese

[mtshiba]

Thank you! I will prepare instructions.

[mtshiba]

I have prepared a multilingualization! Please see /doc/EN/dev_guide/i18n_messages.md for details.