Presents the paywall as an activity on android or a modal in iOS.
Returns a PaywallResult indicating the result of the paywall presentation.
@param offering If set, will present the paywall associated to the given Offering.
@param displayCloseButton Optionally present the paywall with a close button. Only available for original template paywalls. Ignored for V2 Paywalls.
@param customVariables A map of custom variable names to their values. These values can be used for text substitution in paywalls using the {{ custom.variable_name }} syntax.
@param presentationConfiguration Optional configuration for how the paywall is presented on each platform.
Presents the paywall as an activity on android or a modal in iOS as long
as the user does not have the given entitlement identifier active.
Returns a PaywallResult indicating the result of the paywall presentation.
