i18n-json/valid-message-syntax: Add possibility to allow Arrays

[Taucher2003]

Currently it is hardcoded that Arrays can't be a valid translation. However, based on the setup, there are some legitimate usages of Arrays and this is blocking it for no reason.

eslint-plugin-i18n-json/src/valid-message-syntax.js

Lines 143 to 150 in 13d5f18

	} else if (Array.isArray(value)) {
	invalidMessages.push({
	value: ARRAY,
	key,
	path,
	error: new TypeError('An Array cannot be a translation value.')
	});
	} else {

The problem is, that we can't bypass this check with a custom validator which would allow Arrays for some specific keys