Add require script attribute and functionality.

Source/Engine/Scripting/Attributes/Editor/RequireScriptAttribute.cs

@@ -0,0 +1,25 @@
+using System;
+
+namespace FlaxEngine;
+
+/// <summary>
+/// This attribute is used to check for if a script requires another script type.
+/// </summary>
+[Serializable]
+[AttributeUsage(AttributeTargets.Class)]
+public class RequireScriptAttribute : Attribute
+{
+    /// <summary>
+    /// The required type.
+    /// </summary>
+    public Type RequiredType;
+
+    /// <summary>
+    /// Initializes a new instance of the  <see cref="RequireScriptAttribute"/> class.
+    /// </summary>
+    /// <param name="type">The required type.</param>
+    public RequireScriptAttribute(Type type)
+    {
+        RequiredType = type;
+    }
+}