Adding Country Flags to Country Selector

Hey Oscar, first of all thanks for creating this awesome plugin! I am trying to add country flags to the dropdown provided by the plugins shortcode. I see that you have documentation on this: https://www.pricebasedcountry.com/docs/developer-docs/flags-currency-country-switchers-code-snippet/

But it is not clear how to actually implement this code. I tried adding this to functions.php but get an error: syntax error, unexpected '<', expecting end of file

What is the correct way to implement this code? Any guidance would be appreciated.

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