Clarify formatting usage

[toddsmith-adsk]

https://www.i18next.com/translation-function/formatting#basic-usage

Add a comment that the following should use a "semicolon" delimited list of options. It was very easy to overlook the ;

Passing options to the formatting:

1. In the translation string using {{value, formatname(options1: options1Value)}}

[adrai]

feel free to suggest a PR here: https://github.com/i18next/i18next-gitbook/blob/master/translation-function/formatting.md