swift: add «1732. Find the Highest Altitude»

Signed-off-by: Matej Focko <me@mfocko.xyz>

swift/find-the-highest-altitude.swift

@@ -0,0 +1,13 @@
+class Solution {
+    func largestAltitude(_ gain: [Int]) -> Int {
+        var m = 0
+
+        var alt = 0
+        for d in gain {
+            alt += d
+            m = max(m, alt)
+        }
+
+        return m
+    }
+}