WooCommerce Smart Coupons 8.22.0

* Fix: Modifying cron schedule interval only when required
* Fix: Coupon preview under coupon style not visible [WP 5.3+]
* Fix: Changing endpoint setting only appears when Subscription plugin is active
* Update: POT file

* Update: Allow addition of products from coupon action on coupon application even when the cart is empty
* Update: POT file

* Fix: Discount not applied on taxes from AvaTax with Apply before tax setting disabled
* Fix: 'Select options' button not visible for any amount gift certificate product on shop page after adding the gift certificate product into the cart
* Fix: Adding sender email to 'woocommerce_email_header' and 'woocommerce_email_footer' actions while sending an acknowledgment email to sender[WC Standard]
* Fix: Duplicate call to WC_SC_Background_Coupon_Importer::is_process_running in some cases
* Developer: Filter 'wc_sc_linked_coupon_text' to change the text shown for linked coupons on linked product page
* Developer: Filter 'wc_sc_force_show_invalid_coupon' to allow showing of coupons which are invalid due to cart requirements like minimum order total or products
* Developer: Action 'wc_sc_no_available_coupons' to show custom message when no coupons are available for logged-in user
* Tweak: Removing dependency on Action Scheduler library in checking of background process status
* Update: POT file