增加代码API注释文档，整理代码

Scripts/UI/Component/Line.cs

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+using UnityEngine;
+
+namespace XCharts
+{
+    /// <summary>
+    /// The global settings of line chart.
+    /// LineChart的全局配置。
+    /// </summary>
+    [System.Serializable]
+    public class Line
+    {
+        /// <summary>
+        /// the type fo step line.
+        /// 阶梯线图类型。
+        /// </summary>
+        public enum StepType
+        {
+            /// <summary>
+            /// 当前点。
+            /// </summary>
+            Start,
+            /// <summary>
+            /// 当前点和下一个点的中间。
+            /// </summary>
+            Middle,
+            /// <summary>
+            /// 下一个拐点
+            /// </summary>
+            End
+        }
+        [SerializeField] private float m_Tickness;
+        [SerializeField] private bool m_Smooth;
+        [SerializeField] [Range(1f, 10f)] private float m_SmoothStyle;
+        [SerializeField] private bool m_Area;
+        [SerializeField] private bool m_Step;
+        [SerializeField] private StepType m_StepType;
+
+        /// <summary>
+        /// the tickness of lines.
+        /// 线条粗细。
+        /// </summary>
+        public float tickness { get { return m_Tickness; } set { m_Tickness = value; } }
+        /// <summary>
+        /// smoothness.
+        /// 平滑风格。
+        /// </summary>
+        public float smoothStyle { get { return m_SmoothStyle; } set { m_SmoothStyle = value; } }
+        /// <summary>
+        /// Whether the lines are displayed smoothly.
+        /// 是否平滑显示。
+        /// </summary>
+        public bool smooth { get { return m_Smooth; } set { m_Smooth = value; } }
+        /// <summary>
+        /// Whether to show area.
+        /// 是否显示区域填充颜色。
+        /// </summary>
+        public bool area { get { return m_Area; } set { m_Area = value; } }
+        /// <summary>
+        /// Whether to show as a step line. 
+        /// 是否是阶梯线图。
+        /// </summary>
+        public bool step { get { return m_Step; } set { m_Step = value; } }
+        /// <summary>
+        /// the type of step line.
+        /// 阶梯线图类型。
+        /// </summary>
+        public StepType stepTpe { get { return m_StepType; } set { m_StepType = value; } }
+
+        public static Line defaultLine
+        {
+            get
+            {
+                var line = new Line
+                {
+                    m_Tickness = 0.8f,
+                    m_Smooth = false,
+                    m_SmoothStyle = 2f,
+                    m_Area = false,
+                    m_Step = false,
+                    m_StepType = StepType.Middle
+                };
+                return line;
+            }
+        }
+    }
+}