Gets the list of supported currencies that you set for your site.
The getCurrencies() function returns a Promise that resolves to an array of currencies that were set for use in the site using siteSetting.setCurrencies().
This function is different from the getAllCurrencies() function in that it gets only the currencies that have
been set for use in this site using the siteSetting.setCurrencies() function.
The getAllCurrencies() function gets the complete list of all of the currencies that can be supported.
Note: For SiteSettings functions to work, your site must contain a Wix Stores page including the currency conversion element.