feat: i18n support

[nekomeowww]

• [x] i18n help messages
• [x] i18n error message handling
• [x] i18n reply message handling
• [x] i18n prompt with multi-language support
  • [x] #70
• [ ] configurable i18n options (through inline keyboard or whatever)

[OverflowCat]

An i18n library is necessary to manipulate locale strings with ease. Which one would you recommend?

[nekomeowww]

An i18n library is necessary to manipulate locale strings with ease. Which one would you recommend?

I used to use github.com/nicksnyder/go-i18n