chore: add en-GB language

[lincolnthalles]

en-GB is just a copy of en-US, at least for now, but it solves an issue with date format that every now and then some user complain.

en will use the format mm/dd/yyyy, and simply selecting en-GB will format dates as dd/mm/yyyy.

British English

English

[boojack]

If the translation of en-GB will be always the same as en, maybe we can do some hacks. https://github.com/usememos/memos/pull/2865/files#diff-69661a91c7ad27e32735ba8890bfe6547e961e462b5ecf7fc7b11f3329701c79R52

[lincolnthalles]

If the translation of en-GB will be always the same as en, maybe we can do some hacks. https://github.com/usememos/memos/pull/2865/files#diff-69661a91c7ad27e32735ba8890bfe6547e961e462b5ecf7fc7b11f3329701c79R52

Not always, as there are a few differences in wording between British English and American English.

But it's possible to simply leave the json empty and rely on the default en fallback provided by the i18next extension, it just works. This also leaves room for updating in wording, if someone think it's worth it.

The fallbacks object doesn't work in this case. The language must be listed in availableLocales to allow user selection.