RFC - Add documentation for strings and Unicode issues (#636)

* Add documentation for strings and Unicode issues

* More Unicode documentation on character literals and wide characters
diff --git a/docs/advanced/cast/index.rst b/docs/advanced/cast/index.rst
index 36586af..54c1057 100644
--- a/docs/advanced/cast/index.rst
+++ b/docs/advanced/cast/index.rst
@@ -33,6 +33,7 @@
    :maxdepth: 1
 
    overview
+   strings
    stl
    functional
    chrono