Add installation instruction for Swift packages. Update ephemeraHQ/PasskeyAuth.git -> xmtplabs/PasskeyAuth.git

[Sajjon]

• Make clear that the (current) installation instructions are for an Xcode project, update the git url to "xmtplabs/PasskeyAuth.git" instead of "ephemeraHQ/PasskeyAuth.git"
• Add installation instruction for Swift Package (not using Xcode), however, this is blocked by Git tag so that PasskeyAuth can be added as a dependency to a Swift Package #2

[macroscopeapp]

Document Swift Package installation and update repository URL to xmtplabs/PasskeyAuth.git in README.md

Update README.md to add SPM installation instructions for packages and Xcode projects, include a SwiftPM dependency snippet targeting branch main, add a target product dependency example, reorder Requirements to Swift 5.9+, Xcode 14.0+, iOS 16.0+ / macOS 13.0+, and change the repository URL to https://github.com/xmtplabs/PasskeyAuth.git.

📍Where to Start

Start with the Installation section in README.md, reviewing the SPM dependency and target configuration snippets and the updated repository URL.

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Macroscope summarized 44e9c9a.