Feature Request: Add interpolation validation

[justinaray]

Our translation team has been known to accidentally translate replacement tokens. It would be awesome if this lib could parse the format and consistency of interpolation tokens. Bonus points if we could support ICU plurals in the replacements; but, I realize this is probably an entirely different ticket and feature as it looks like i18n prefers the plural suffixes by default.

// en.json { "hello": "hello {{name}}" } // es.json { "hello": "hola {{nombre}} }