feat: backporting existing raylib-cs examples and new official raylib examples to WASM, adopting raylib's original code style

Examples/ExcludeFromBrowserAttribute.cs

@@ -0,0 +1,17 @@
+namespace Examples;
+
+/// <summary>
+/// Marks an <see cref="IExample"/> that is omitted from the browser host (Web/Host.cs)
+/// because of a wasm/WebGL platform limitation. Desktop runs are unaffected.
+/// </summary>
+[AttributeUsage(AttributeTargets.Class, Inherited = false)]
+public sealed class ExcludeFromBrowserAttribute : Attribute
+{
+    /// <summary>Why the example cannot run in the browser.</summary>
+    public string Reason { get; }
+
+    public ExcludeFromBrowserAttribute(string reason = null)
+    {
+        Reason = reason;
+    }
+}