Add timestamp screenshot for MacOS on debugging UI

src/main/java/wtf/beatrice/autosqueal/util/SystemUtil.java

@@ -0,0 +1,24 @@
+package wtf.beatrice.autosqueal.util;
+
+import java.util.Locale;
+
+public class SystemUtil
+{
+
+    public static OperatingSystem getHostSystem() {
+        String osName = System.getProperty("os.name").toLowerCase(Locale.ENGLISH);
+        if (osName.contains("win")) {
+            return OperatingSystem.WINDOWS;
+        } else if (osName.contains("nix") || osName.contains("nux")) {
+            return OperatingSystem.LINUX;
+        } else if (osName.contains("mac")) {
+            return OperatingSystem.MAC_OS;
+        } else {
+            return OperatingSystem.UNKNOWN;
+        }
+    }
+
+    public enum OperatingSystem {
+        WINDOWS, LINUX, MAC_OS, UNKNOWN;
+    }
+}