feat: 添加端口代理类型转换工具

PortProxyTool/PortProxyUtil.cs

@@ -0,0 +1,16 @@
+namespace PortProxyTool;
+
+internal static class PortProxyUtil
+{
+    public static PortProxyType? GetPortProxyTypeByString(string type)
+    {
+        return type.ToLower() switch
+        {
+            "v4tov4" => PortProxyType.V4ToV4,
+            "v4tov6" => PortProxyType.V4ToV6,
+            "v6tov6" => PortProxyType.V6ToV6,
+            "v6tov4" => PortProxyType.V6ToV4,
+            _ => null
+        };
+    }
+}