support for ICU Format in i18n

**Node version**: v18
**Sails version** _(sails)_: 1.4.0
**ORM hook version** _(sails-hook-orm)_:
**Sockets hook version** _(sails-hook-sockets)_:
**Organics hook version** _(sails-hook-organics)_:
**Grunt hook version** _(sails-hook-grunt)_:
**Uploads hook version** _(sails-hook-uploads)_:
**DB adapter & version** _(e.g. sails-mysql@5.55.5)_:
**Skipper adapter & version** _(e.g. skipper-s3@5.55.5)_:

sails uses i18n-2 which seems have no support for [ICU Message Formatting](https://lokalise.com/blog/complete-guide-to-icu-message-format/)
and we have a strict requirement to use translation file(json files) in ICU Format only.
but i could not find any doc to add support for ICU message format in Sails

The issue names Sails' i18n integration and its i18n-2 dependency but no files or tests. Start by tracing how Sails loads translation JSON and how i18n-2 formats messages, then define the required ICU behavior and documentation or tests that would demonstrate support.

Written by the indexing model from the issue text.