Add **Web platform with Emscripten**

Source/Engine/Platform/Web/WebThread.h

@@ -0,0 +1,63 @@
+// Copyright (c) Wojciech Figat. All rights reserved.
+
+#pragma once
+
+#if PLATFORM_WEB
+
+#include "../Base/ThreadBase.h"
+
+/// <summary>
+/// Thread object for Web platform.
+/// </summary>
+class FLAXENGINE_API WebThread : public ThreadBase
+{
+public:
+    /// <summary>
+    /// Initializes a new instance of the <see cref="WebThreadThread"/> class.
+    /// </summary>
+    /// <param name="runnable">The runnable.</param>
+    /// <param name="name">The thread name.</param>
+    /// <param name="priority">The thread priority.</param>
+    WebThread(IRunnable* runnable, const String& name, ThreadPriority priority)
+        : ThreadBase(runnable, name, priority)
+    {
+    }
+    
+public:
+    /// <summary>
+    /// Factory method to create a thread with the specified stack size and thread priority
+    /// </summary>
+    /// <param name="runnable">The runnable object to execute</param>
+    /// <param name="name">Name of the thread</param>
+    /// <param name="priority">Tells the thread whether it needs to adjust its priority or not. Defaults to normal priority</param>
+    /// <param name="stackSize">The size of the stack to create. 0 means use the current thread's stack size</param>
+    /// <returns>Pointer to the new thread or null if cannot create it</returns>
+    static WebThread* Create(IRunnable* runnable, const String& name, ThreadPriority priority = ThreadPriority::Normal, uint32 stackSize = 0)
+    {
+        return New<WebThread>(runnable, name, priority);
+    }
+
+public:
+    // [ThreadBase]
+    void Join() override
+    {
+        // TOOD: impl this
+    }
+
+protected:
+    // [ThreadBase]
+    void ClearHandleInternal() override
+    {
+        // TOOD: impl this
+    }
+    void SetPriorityInternal(ThreadPriority priority) override
+    {
+        // TOOD: impl this
+    }
+    void KillInternal(bool waitForJoin) override
+    {
+        // TOOD: impl this
+    }
+};
+
+#endif