Save the `converter.php` file to a publicly accessible directory. Require this file in your functions along with adding the two lines of code in `functions.php`

Only requirement is `rosell-dk/webp-convert`, install by running `composer require rosell-dk/webp-convert` and requiring `autoload.php` somewhere in your installaton - you don't need to worry about requiring `autoload.php` if using Bedrock