[codex] Add POP to My WordPress apps

[mircobabini]

Summary

• add the WordPress.org POP plugin slug to the My WordPress curated plugin catalog
• point installs to POP's setup wizard so users land on an actionable first-run screen
• disclose that POP requires a POP account and that the free plan includes 20 API credits per month

Why

POP is already approved in the WordPress.org Plugin Directory and gives My WordPress users a focused electronic invoicing option for WooCommerce and broader WordPress payment flows.

Validation

• ran npm run validate:my-wordpress-json

Notes

• plugin slug: woopop-electronic-invoice-free
• plugin page: https://wordpress.org/plugins/woopop-electronic-invoice-free/
• POP account required for the core flow; paid plans unlock additional compliance and delivery features
• submission follows blueprints/my-wordpress/submitting-plugins-and-apps.md as a plugin entry, not a full app blueprint