Xcode project with RevenueCatUI + Tests

[jamesrb1]

RevenueCatUI and its tests are now accessible in the files navigator:

It add two new schemes:

Use RevenueCatUIDev to build RevenueCatUI, and RevenueCatUITests to run its tests.

Linting works:

Individual tests can be run from the UI:

N.B.

• Tests must be run via the RevenueCatUITest scheme.
• Xcode sometimes has difficulties switching schemes. If you see the errors below, clean the build folder and try again and it will work
• Building with the RevenueCatUIDev scheme creates some warnings related to switches. Adding in an @unknown default: resolves the warning but causes an error in other configurations ("Default will never be executed").
• Because the root Package file was not altered, this PR won't have any affect on how our package works when integrated via SPM.

[RevenueCat-Danger-Bot]

	1 Warning
:warning:	This PR increases the size of the repo by more than 100.00 KB (increased by 102.31 KB).

Generated by :no_entry_sign: Danger