Updated Quickstart (markdown)

Quickstart.md

@@ -122,7 +122,7 @@ Add to end of main loop:
 // (Your code clears your framebuffer, renders your stuff etc.)
 ImGui::Render();
 ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
-// (Your call calls glfwSwapBuffers() etc.)
+// (Your code calls glfwSwapBuffers() etc.)
 ```
 Add to Shutdown:
 ```cpp
@@ -131,3 +131,60 @@ ImGui_ImplGlfw_Shutdown();
 ImGui::DestroyContext();
 ```
 That should be all!
+
+## Example: If you are using SDL2 + OpenGL/WebGL
+
+Full standalone example: [example_sdl2_opengl3/main.cpp](https://github.com/ocornut/imgui/blob/master/examples/example_sdl2_opengl3/main.cpp)
+
+Add to Includes:
+```cpp
+#include "imgui.h"
+#include "imgui_impl_sdl2.h"
+#include "imgui_impl_opengl3.h"
+```
+Add to Initialization:
+```cpp
+// Setup Dear ImGui context
+IMGUI_CHECKVERSION();
+ImGui::CreateContext();
+ImGuiIO& io = ImGui::GetIO();
+io.ConfigFlags |= ImGuiConfigFlags_NavEnableKeyboard;     // Enable Keyboard Controls
+io.ConfigFlags |= ImGuiConfigFlags_NavEnableGamepad;      // Enable Gamepad Controls
+io.ConfigFlags |= ImGuiConfigFlags_DockingEnable;         // IF using Docking Branch
+
+// Setup Platform/Renderer backends
+ImGui_ImplSDL2_InitForOpenGL(window, YOUR_SDL_GL_CONTEXT);
+ImGui_ImplOpenGL3_Init();
+```
+Add to start of main loop:
+```cpp
+// (Where your code calls SDL_PollEvent())
+ImGui_ImplSDL2_ProcessEvent(&event); // Forward your event to backend
+
+// (After event loop)
+// Start the Dear ImGui frame
+ImGui_ImplOpenGL3_NewFrame();
+ImGui_ImplSDL2_NewFrame();
+ImGui::NewFrame();
+ImGui::ShowDemoWindow(); // Show demo window :)
+```
+Add to end of main loop:
+```cpp
+// Rendering
+// (Your code clears your framebuffer, renders your stuff etc.)
+ImGui::Render();
+ImGui_ImplOpenGL3_RenderDrawData(ImGui::GetDrawData());
+// (Your code calls SDL_GL_SwapWindow() etc.)
+```
+Add to Shutdown:
+```cpp
+ImGui_ImplOpenGL3_Shutdown();
+ImGui_ImplSDL2_Shutdown();
+ImGui::DestroyContext();
+```
+That should be all!
+
+## Example: If you are using another combination of backends?
+
+The various examples above should reflect integration with a majority of backends, so you can follow the same logic.
+Some backends require more information from you (e.g. in particular Vulkan and DirectX12 rendering backends). In doubt, refers to the corresponding [examples](https://github.com/ocornut/imgui/tree/master/examples) application.