* Add support for pmpro-card classes

[MaximilianoRicoTabo]

• Remove id that's error prone and not needed
• A bit of WPCS

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[kimcoleman]

Reworked this HTML and now using pmpro_get_element_class.

Note in my testing there is an issue with free levels and donations. If you have a free level and the minimum donation amount is $0, the PBC choose a payment method never appears. We probably need to add a listener just like https://github.com/strangerstudios/pmpro-donations/blob/dev/includes/checkout.php#L132-L143 somewhere.