Update Japanese translation

I am currently working on the Japanese README, improving unnatural translations and adding new ones.

The working branch is [here](https://github.com/Hayao0819/Typora-i18n/tree/new-jp)

## text labels  for which the context is not known

- `"Code Block Math  (```math code block)"` in `Panel.strings`
- `Hard line wrap` in `Panel.strings`
- `Preserve tabs` in `Panel.strings`

