WooCommerce Product Vendors 2.2.7

* Add - New action on Vendor Profile screen, `wcpv_vendor_settings_render_additional_fields`, to enable other plugins to add additional settings fields.
* Fix - Ensure array key exists before we try using it.
* Fix - Ensure the data we are using is an array before we try accessing a property of that array.

* Fix - Column width and characters break issues when viewing the product list table on narrow screen sizes.
* Fix - Ensure the Vendor Email field is required properly and if not set for existing Vendors, show an admin notice.
* Tweak - Add more details to log messages coming from PayPal.

* Add - Approval instruction to the email sent to store owner when new vendors submit applications.
* Add - Approve action to approve pending vendors from the user list table.
* Add - If a customer leaves notes when placing an order, show those notes in the vendor emails and the vendor order dashboard.
* Fix - Add customer's billing address to the vendor notification emails.
* Fix - Ensure our query filter only runs on the main query.
* Fix - Use an integer for the menu position to avoid conflicts with other menus.
* Tweak - WC 5.4 compatibility.
* Tweak - WP 5.7 compatibility.