Add to nav bar

Author: mborland

doc/modules/ROOT/nav.adoc

@@ -11,6 +11,7 @@
 *** xref:examples.adoc#examples_fmt_format[pass:[{fmt}]]
 *** xref:examples.adoc#examples_std_format[`<format>`]
 *** xref:examples.adoc#examples_print[`<print>`]
+** xref:examples.adoc#examples_file[Read and Write to File]
 * xref:financial_examples.adoc[]
 ** xref:financial_examples.adoc#examples_money_parsing[Parsing Pricing Data from File]
 ** xref:financial_examples.adoc#examples_boost_math[Boost.Math Integration]