Add vertical layout toggle to playground

[yuki-stripe]

Summary

Adds the toggle and a dummy placeholder API.

Future PRs will update the placeholder API to a real (but internal) API and, of course, make the toggle do something :)

Motivation

Keep the PRs small

[github-actions]

⚠️ Public API changes detected:

StripePayments

- @objc public var allowRedisplay: StripePayments.STPPaymentMethodAllowRedisplay
- @objc convenience public init(card: StripePayments.STPPaymentMethodCardParams, billingDetails: StripePayments.STPPaymentMethodBillingDetails?, allowRedisplay: StripePayments.STPPaymentMethodAllowRedisplay = .unspecified, metadata: [Swift.String : Swift.String]?)
+ @objc convenience public init(card: StripePayments.STPPaymentMethodCardParams, billingDetails: StripePayments.STPPaymentMethodBillingDetails?, metadata: [Swift.String : Swift.String]?)
- @objc convenience public init(usBankAccount: StripePayments.STPPaymentMethodUSBankAccountParams, billingDetails: StripePayments.STPPaymentMethodBillingDetails, allowRedisplay: StripePayments.STPPaymentMethodAllowRedisplay = .unspecified, metadata: [Swift.String : Swift.String]?)
+ @objc convenience public init(usBankAccount: StripePayments.STPPaymentMethodUSBankAccountParams, billingDetails: StripePayments.STPPaymentMethodBillingDetails, metadata: [Swift.String : Swift.String]?)
- case unspecified
- case limited
- case always
- public init?(rawValue: Swift.Int)
- public typealias RawValue = Swift.Int
- public var rawValue: Swift.Int {
- get
- }

If you are adding a new public API consider the following:

• Do these APIs need to be public or can they be protected with @_spi(STP)?
• If these APIs need to be public, assess whether they require an API review.

If you are modifying or removing a public API:

• Does this require a breaking version change?
• Do these changes require API review?

If you confirm these APIs need to be added/updated and have undergone necessary review, add the label modifies public API to this PR to acknowledge and bypass this check.

[porter-stripe]

I'm guessing the bot is leaving a comment about the public APIs since the branch it out of date w/ master?

[yuki-stripe]

I'm guessing the bot is leaving a comment about the public APIs since the branch it out of date w/ master?

@porter-stripe Hmm I guess so. Should we tweak the script? O/w I'd think this would trigger often.

[porter-stripe]

@yuki-stripe I'll look into modifying the script to look at the first commit from when the branch was started rather than current master. But it gets me thinking, maybe we shouldn't allow merging into master if your branch isn't up to date with master. I could imagine a scenario where something could break, and technically the bitrise build is building an out of date build since it doesn't have the latest changes in master, unless it's merging the changes during the build?