增加Tooltip的Auto自动设置显示类型和触发类型

Runtime/Internal/Attributes/DefaultTooltipAttribute.cs

@@ -0,0 +1,17 @@
+using System;
+
+namespace XCharts.Runtime
+{
+    [AttributeUsage(AttributeTargets.Class, AllowMultiple = true)]
+    public sealed class DefaultTooltipAttribute : Attribute
+    {
+        public readonly Tooltip.Type type;
+        public readonly Tooltip.Trigger trigger;
+
+        public DefaultTooltipAttribute(Tooltip.Type type, Tooltip.Trigger trigger)
+        {
+            this.type = type;
+            this.trigger = trigger;
+        }
+    }
+}