Extend map to support mapping to object key paths.

SwiftTipKeypathMapping.swift

extension Sequence {
    func map<T>(_ keyPath: KeyPath<Element, T>) -> [T] {
        return self.map {
            $0[keyPath: keyPath]
        }
    }
}

struct Transaction {
    let amount: Double
    let originAddress: String
}

let transactions: [Transaction] = [
    .init(amount: 14.53,
          originAddress: "1BvBMSEYstWetqTFn5Au4m4GFg7xJaNVN2"),
    .init(amount: 344.15,
          originAddress: "3J98t1WpEZ73CNmQviecrnyiWrnqRhWNL")
]

print("""
    💳 Transactions from addresses
    \(transactions.map(\.originAddress).joined(separator: ", "))
    sent funds totaling
    💵 \(transactions.map(\.amount).reduce(0, +))
""")