Improve train status formatting

This change adds proper singular/plural labels for minutes and hours in the lateness display, fixes green status text contrast for dark mode, and updates the README to credit the Amtrak.js models used as a base.

Sources/AmtrakStatus/ContentView.swift

@@ -103,7 +103,7 @@ struct ContentView: View {
     func statusColour(_ color: Color) -> Color {
         switch color {
         case .green:
-            return .black
+            return .adaptive(light: .white, dark: .black)
         default:
             return .white
         }

Sources/AmtrakStatus/Helper.swift

@@ -0,0 +1,7 @@
+import Foundation
+
+extension Int {
+    func pluralized(singular: String, plural: String) -> String {
+        self == 1 ? singular : plural
+    }
+}

Sources/AmtrakStatus/TrainLateness.swift

@@ -33,13 +33,17 @@ enum TrainLateness {
         }
     }
     
-    
     static func formatted(_  minutes: Int) -> String {
         let hours = minutes / 60
         let remainder = minutes % 60
+    
+        let minutesPart = "\(minutes) \(minutes.pluralized(singular: "min", plural: "mins"))"
+        let hoursPart = "\(hours) \(hours.pluralized(singular: "hr", plural: "hrs"))"
+        
         guard hours > 0 else {
-            return "\(minutes) mins"
+            return minutesPart
         }
-        return "\(hours) hrs"
+        
+        return hoursPart
     }
 }