Added a hello world example to the OpenGL guide (#32670)

* Added hello world example to OpenGL guide

* Fixed command

* Fixed command

* Added command for building

* Update index.md

guide/english/game-development/opengl/helloworld/index.md

@@ -0,0 +1,69 @@
+---
+title: Hello World
+---
+# Hello World
+
+This is a Hello World application of OpenGL
+
+```C
+ #include <GLFW/glfw3.h>
+
+GLFWwindow* window = NULL;
+
+int main(void)
+{
+    // Initialize GLFW
+    if (!glfwInit())
+        return -1;
+
+    // Create window with dimensions 640 x 480
+    window = glfwCreateWindow(640, 480, "Hello World", NULL, NULL);
+    if (!window)
+    {
+        glfwTerminate();
+        return -1;
+    }
+
+    // Make the window to the current OpenGL context
+    glfwMakeContextCurrent(window);
+
+    // Loop until the window gets closed
+    while (!glfwWindowShouldClose(window))
+    {
+        // Clear Screen with default color black
+        glClear(GL_COLOR_BUFFER_BIT);
+
+        // Render triangle
+        glBegin(GL_TRIANGLES);
+        // Left Down
+        glColor3f(1.0f,0.0,0.0f);
+        glVertex2f(-0.5f,-0.5f);
+        // Right Down
+        glColor3f(0.0f,1.0,0.0f);        
+        glVertex2f( 0.5f,-0.5f);
+        // Mid Up
+        glColor3f(0.0f,0.0f,1.0f);        
+        glVertex2f( 0.0f, 0.5f);
+        glEnd();
+
+        // Swap Buffers to render the new frame to the window
+        glfwSwapBuffers(window);
+
+        // Poll events to get the window close event
+        glfwPollEvents();
+    }
+
+    // Terminate GLFW
+    glfwTerminate();
+    return 0;
+}
+```
+
+This code renders a triangle to a black window. To build this example you need the library [GLFW](https://www.glfw.org). <br>
+```
+sudo apt-get install libglfw3-dev
+```
+To build it just run <br>
+```
+gcc -o hello_world source.c -lglfw -lGL
+```