WooCommerce Bookings Availability 1.2.8

* Fix - Popover container on calendar block obscured when Gutenberg plugin is active.
* Tweak - Remove set width of products selection screen to expand to container.
* Tweak - WC 4.9 compatibility.
* Tweak - WP 5.6 compatibility.

* Fix - Weekly calendar block times are incorrect.
* Tweak - Filter for block parameters to e.g. allow overriding of checkout URL.
* Fix - `Book now` button changes to `Sold Out` for a split second.

* Tweak - WordPress 5.5 compatibility.