Show Buttons in entity editor

- ScriptEngine: Added HasCustomAttribute- extension method
- ScriptEngine: Added Application class

ScriptCore/Editor/ShowButtonAttribute.cs

@@ -0,0 +1,42 @@
+
+using System;
+
+namespace GlitchyEngine.Editor;
+
+public enum ButtonVisibility
+{
+    /// <summary>
+    /// The button will be visible in edit mode.
+    /// </summary>
+    InEditMode = 1,
+    /// <summary>
+    /// The button will be visible in play mode.
+    /// </summary>
+    InPlayMode = 2,
+    /// <summary>
+    /// The button will always be visible.
+    /// </summary>
+    Always = InEditMode | InPlayMode
+}
+
+/// <summary>
+/// Specifies that a button will be shown in the editor that, when clicked, executes the method this attribute is attached to.
+/// </summary>
+[AttributeUsage(AttributeTargets.Method)]
+public sealed class ShowButtonAttribute : Attribute
+{
+    /// <summary>
+    /// The text on the button.
+    /// </summary>
+    public string ButtonText { get; private set; }
+
+    /// <summary>
+    /// Determines whether the button is visible in edit and/or play mode.
+    /// </summary>
+    public ButtonVisibility Visibility { get; set; } = ButtonVisibility.Always;
+
+    public ShowButtonAttribute(string buttonText)
+    {
+        ButtonText = buttonText;
+    }
+}