Fix compilation on case-sensitive filesystems (#463)

diff --git a/examples/executable_dll_and_plugin/main.cpp b/examples/executable_dll_and_plugin/main.cpp
index 930efc0..0955091 100644
--- a/examples/executable_dll_and_plugin/main.cpp
+++ b/examples/executable_dll_and_plugin/main.cpp
@@ -24,7 +24,7 @@
 #ifdef _WIN32
 #define WIN32_LEAN_AND_MEAN
 DOCTEST_MAKE_STD_HEADERS_CLEAN_FROM_WARNINGS_ON_WALL_BEGIN
-#include <Windows.h>
+#include <windows.h>
 DOCTEST_MAKE_STD_HEADERS_CLEAN_FROM_WARNINGS_ON_WALL_END
 #ifdef _MSC_VER
 #define LoadDynamicLib(lib) LoadLibrary(lib ".dll")