macos: add string extension

macos/Sources/Helpers/String+Extension.swift

@@ -0,0 +1,18 @@
+extension String {
+    func truncate(length: Int, trailing: String = "…") -> String {
+        let maxLength = length - trailing.count
+        guard maxLength > 0, !self.isEmpty, self.count > length else {
+            return self
+        }
+        return self.prefix(maxLength) + trailing
+    }
+    
+    func temporaryFile(_ filename: String = "temp") -> URL {
+        let url = FileManager.default.temporaryDirectory
+            .appendingPathComponent(filename)
+            .appendingPathExtension("txt")
+        let string = self
+        try? string.write(to: url, atomically: true, encoding: .utf8)
+        return url
+    }
+}