LearnDash LMS Stripe Integration Addon 1.9.3

* Fixed load specific js-cookie version for Stripe SCA compatibility

* Added dependencies check
* Added allow_promotion_codes arg in Stripe session creation API
* Updated add 'customer' arg in Stripe session API so that Stripe only create 1 customer object for each WP user
* Fixed token used more than once error on legacy checkout
* Fixed fatal error due to uncaught Stripe API Exception
* Fixed Stripe JS is loaded multiple times if there's multiple payment button on a page

Added support for older browsers
Updated force load jquery dependency on frontend
Fixed wrong purchase button label for groups