Fix README and remove git diff from main.cpp

Author: zmertens

examples/example_sdl3_opengl3/README.md

@@ -1,4 +1,42 @@
-# Example SDL3 with OpenGL3
+# How to Build
+
+## Windows with Visual Studio's IDE
+
+Use the provided project file (.vcxproj). Add to solution (imgui_examples.sln) if necessary.
+
+## Windows with Visual Studio's CLI
+
+Use build_win32.bat or directly:
+```
+set SDL2_DIR=path_to_your_sdl3_folder
+cl /Zi /MD /utf-8 /I.. /I..\.. /I%SDL2_DIR%\include main.cpp ..\..\backends\imgui_impl_sdl3.cpp ..\..\backends\imgui_impl_opengl3.cpp ..\..\imgui*.cpp /FeDebug/example_sdl3_opengl3.exe /FoDebug/ /link /libpath:%SDL2_DIR%\lib\x86 SDL3.lib opengl32.lib /subsystem:console
+#                 ^^ include paths     ^^ source files                                                                                    ^^ output exe                    ^^ output dir   ^^ libraries
+# or for 64-bit:
+cl /Zi /MD /utf-8 /I.. /I..\.. /I%SDL2_DIR%\include main.cpp ..\..\backends\imgui_impl_sdl3.cpp ..\..\backends\imgui_impl_opengl3.cpp ..\..\imgui*.cpp /FeDebug/example_sdl3_opengl3.exe /FoDebug/ /link /libpath:%SDL2_DIR%\lib\x64 SDL3.lib SDL2mainopengl32.lib /subsystem:console
+```
+
+## Linux and similar Unixes
+
+Use our Makefile or directly:
+```
+c++ `sdl3-config --cflags` -I .. -I ../.. -I ../../backends
+  main.cpp ../../backends/imgui_impl_sdl3.cpp ../../backends/imgui_impl_opengl3.cpp ../../imgui*.cpp
+  `sdl3-config --libs` -lGL -ldl
+```
+
+## macOS
+
+Use our Makefile or directly:
+```
+brew install sdl3
+c++ `sdl3-config --cflags` -I .. -I ../.. -I ../../backends
+  main.cpp ../../backends/imgui_impl_sdl3.cpp ../../backends/imgui_impl_opengl3.cpp ../../imgui*.cpp
+  `sdl3-config --libs` -framework OpenGl -framework CoreFoundation
+```
+
+## Emscripten
+
+As of 2023-05-30 Emscripten doesn't support SDL3 yet.
 
 ## Android
 

examples/example_sdl3_opengl3/main.cpp

@@ -11,14 +11,10 @@
 #include "imgui_impl_sdl3.h"
 #include "imgui_impl_opengl3.h"
 #include <stdio.h>
-<<<<<<< HEAD
-#include <SDL3/SDL.h>
-=======
 
 #include <SDL3/SDL.h>
 #include <SDL3/SDL_main.h>
 
->>>>>>> e54b3b42 (Update CMakeLists.txt to download properly)
 #if defined(IMGUI_IMPL_OPENGL_ES2)
 #include <SDL3/SDL_opengles2.h>
 #else