add support for switch-case output

[ivanhofer]

Similar tho the {select} format in the ICU-syntax, typesafe-i18n should be able to handle switch-case options.
Main use-case is something like gender-related output, but it could be used for uther use-cases too.

I propose this could look like:

named keys

{0}, {1}, {2}, ...

const en = {
   response: '{gender|[male:He,female:She,other:They]} will respond shortly.'
}

LL.response({ gender: 'male' }) => 'He will respond shortly'

index-based keys

{key}, {key2}, ...

const en = {
   response: '{0|[male:He,female:She,other:They]} will respond shortly.'
}

LL.response('female') => 'She will respond shortly'

better readability trough spacing

Spacing is allowed and will be trimmed before inserting it into the sentence.

const en = {
   response: '{0 | [ male: He, female: She, other: They ] } will respond shortly.'
}

LL.response('other') => 'They will respond shortly'

default case

A default-case should be marked with *

const en = {
   response: '{0 | [ male: He, female: She, other: They ] } will respond shortly.',
   response2: '{0 | [ male: He, female: She, *: They ] } will respond shortly.'
}

LL.response('other') => 'They will respond shortly'
LL.response(null) // => TypeScript Error

LL.response2('other') => 'They will respond shortly'
LL.response2(null) // => 'They will respond shortly'

formatter chaining

It should be possible to chain it and pass it to another formatter

const en = {
   response: '{gender | [ male: He, female: She, other: They ] | uppercase } will respond shortly.'
}

LL.response({ gender :'male' }) => 'HE will respond shortly'

typesafety

This should be implemented in a typesafe way, so you would also need to pass the same options for all other translations.

const en = {
   response: '{gender | [ male: He, female: She, other: They ] | uppercase } will respond shortly.'
}
const de = {
   response: '{gender | [ male: Er wird, female: Sie wird, other: Sie werden ]} in Kürze antworten.'
}
const it = {
   response: '{gender | [ male: Lui, female: Lei ]} risponderà a breve.' // => TypeScript Error: 'other' is missing
}

[abastardi]

This looks really good. One minor aesthetic suggestion -- as it is common for braces to represent objects/maps and brackets to represent lists/arrays, maybe wrap the key/value map in braces rather than brackets:

{ 0 | { male: He, female: She, other: They } }

[ivanhofer]

I wasn't sure about that first, so I have chosen the array brackets. But the more I think about it I also prefer the object syntax. Thanks for your feedback

[ivanhofer]

added in version 2.55.0