LibCore: Add System::sleep_ms

Author: https://github.com/stasoid
Commit: a291a7f770
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/2917
Reviewed-by: https://github.com/ADKaster ✅

Libraries/LibCore/SystemWindows.cpp

@@ -225,4 +225,10 @@ bool is_socket(int handle)
     return GetFileType(to_handle(handle)) == FILE_TYPE_PIPE;
 }
 
+ErrorOr<void> sleep_ms(u32 milliseconds)
+{
+    Sleep(milliseconds);
+    return {};
+}
+
 }