YITH WooCommerce Stripe Premium 3.20.0

* New: Support for WooCommerce 4.1
* New: added line details for Stripe Checkout
* Update: plugin framework
* Update: Stripe PHP library to version 7.31.0
* Tweak: added error message when manual renew attempt fails
* Tweak: moved "retry invoice with other cards" procedure after suspension handling
* Tweak: removed deprecated param from subscription API
* Tweak: retrieve gateway using proper methods
* Fix: issue with charge retrieval during dispute webhook handling
* Fix: payment intent not being refreshed when original order is cancelled and a new one with same amount is being attempted
* Fix: issue with free item when creating Checkout session
* Fix: issue with short description of the item when creating checkout session
* Dev: added filter yith_wcstripe_checkout_session_detailed_line_items to disable line details on Stripe Checkout
* Dev: added yith_wcstripe_session_param filter

* New: support for WordPress 4.0
* New: support for WooCommerce 4.0
* New: support for API 2020-03-02
* Update: Stripe PHP library to version 7.27.2
* Update: plugin framework
* Update: Spanish language
* Fix: prevent notice when paying renews
* Fix: process_refund method now correctly process refunds on shipping items (thanks to Alex)

* New: support for WooCommerce 3.9
* Update: plugin framework
* Update: Stripe library to version 7.14.2
* Update: Stripe API to version 2019-12-03
* Tweak: add some log in renew subscription process
* Fix: notice when visiting stripe_webhook api endpoint directly
* Fix: Removed usage of Stripe\Exception\ApiErrorException::factory; using new Exception instead
* Fix: issue with renew payment for guest users