FAQ about backslashes in string literal since the one in main.cpp isn't being noticed enough. (#1397)

imgui.cpp

@@ -547,11 +547,15 @@
 
  Q: How can I load a different font than the default? (default is an embedded version of ProggyClean.ttf, rendered at size 13)
  A: Use the font atlas to load the TTF/OTF file you want:
-
       ImGuiIO& io = ImGui::GetIO();
       io.Fonts->AddFontFromFileTTF("myfontfile.ttf", size_in_pixels);
       io.Fonts->GetTexDataAsRGBA32() or GetTexDataAsAlpha8()
 
+    New programmers: remember that in C/C++ and most programming languages if you want to use a backslash \ in a string literal you need to write a double backslash "\\":
+      io.Fonts->AddFontFromFileTTF("MyDataFolder\MyFontFile.ttf", size_in_pixels);   // WRONG
+      io.Fonts->AddFontFromFileTTF("MyDataFolder\\MyFontFile.ttf", size_in_pixels);  // CORRECT
+      io.Fonts->AddFontFromFileTTF("MyDataFolder/MyFontFile.ttf", size_in_pixels);   // ALSO CORRECT
+
  Q: How can I easily use icons in my application?
  A: The most convenient and practical way is to merge an icon font such as FontAwesome inside you main font. Then you can refer to icons within your 
     strings. Read 'How can I load multiple fonts?' and the file 'misc/fonts/README.txt' for instructions and useful header files.