Examples Refactor: GLFW: Explicit functions to init GLFW with OpenGL or Vulkan since we cannot read the api hints from glfw.

examples/opengl2_example/main.cpp

@@ -31,7 +31,7 @@ int main(int, char**)
     ImGui::CreateContext();
     ImGuiIO& io = ImGui::GetIO(); (void)io;
     //io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;  // Enable Keyboard Controls
-    ImGui_ImplGlfw_Init(window, true);
+    ImGui_ImplGlfw_InitForOpenGL(window, true);
     ImGui_ImplOpenGL2_Init();
 
     // Setup style