The Events Calendar - Virtual Events 1.15.6

* Version - The minimum supported version of WordPress is now 6.1.0
* Fix - Ensure the block editor includes support for user-defined custom CSS classes. [TEC-4724]
* Fix - Fix for error `Publishing failed. The _tribe_events_virtual_show_embed_to property has an invalid stored value, and cannot be updated to null` when editing an event in the block editor. This was caused by an invalid REST arg type definition. [VE-574]
* Fix - Ensure that the Virtual Event button link within the Tickets Emails template is the correct color. [ET-1785]
* Tweak - Changed views: `blocks/virtual-event`, `integrations/event-tickets/emails/template-parts/header/head/ve-styles`
* Language - 0 new strings added, 2 updated, 0 fuzzied, and 0 obsoleted.

* Version - Virtual Events 1.15.1 is only compatible with The Events Calendar 6.1.2 and higher
* Version - Virtual Events 1.15.1 is only compatible with Events Tickets 5.6.1 and higher
* Fix - Lock our container usage(s) to the new Service_Provider contract in tribe-common. This prevents conflicts and potential fatals with other plugins that use a di52 container.

* Feature - Include Virtual Events compatibility for the new Tickets Emails feature.
* Tweak - Added filters: `tec_events_virtual_ticket_email_url`
* Tweak - Changed views: `integrations/event-tickets/emails/template-parts/body/virtual-event/link`, `integrations/event-tickets/emails/template-parts/header/head/ve-styles`
* Language - 2 new strings added, 14 updated, 0 fuzzied, and 0 obsoleted