Added ArgumentParser to main project

- At Swift book's Functions and Closure section in Playgrounds (next up Objects and Classes)

SwiftyFox.playground/Contents.swift

@@ -1,22 +1,28 @@
 import Cocoa
 
-let interestingNumbers = [
-    "Prime": [2, 3, 5, 7, 11, 13],
-    "Fibonacci": [1, 1, 2, 3, 5, 8],
-    "Square": [1, 4, 9, 16, 25],
-];
+func greet(_ person: String, on day: String) -> String {
+    return "Hello \(person), today is \(day)."
+}
 
-var largest = 0
+// "Hello Tony Bark, today is Tuesday."
+greet("Tony Bark", on: "Tuesday")
 
-for (_, numbers) in interestingNumbers {
-    for number in numbers {
-        if number > largest {
-            largest = number // 25
+func calcStats(scores: [Int]) -> (min: Int, max: Int, sum: Int) {
+    var min = scores[0]
+    var max = scores[0]
+    var sum = 0
+    
+    for score in scores {
+        if score > max {
+            max = score
+        } else if score < min {
+            min = score
         }
+        sum += score
     }
+    
+    return (min, max, sum)
 }
 
-var total = 0
-for i in 0..<4 {
-    total += i // 6
-}
+let stats = calcStats(scores: [5, 3, 100, 3, 9])
+let sum = stats.sum // 120