Add Pronamic Pay default payment methods integration

[Copilot]

Integrates the pronamic/pronamic-pay-default-payment-methods package and bumps the wp-pay/core minimum version requirement.

Changes

• composer.json — Added pronamic/pronamic-pay-default-payment-methods: ^1.0 dependency; bumped wp-pay/core from ^4.32 to ^4.33
• pronamic-ideal.php — Bootstraps the new package alongside existing plugin instances:

\Pronamic\PronamicForms\Plugin::instance();

\Pronamic\PronamicPayDefaultPaymentMethods\Plugin::instance();