Improve benchmark nav

Author: mborland

doc/modules/ROOT/nav.adoc

@@ -41,9 +41,9 @@
 * xref:limits.adoc[]
 * xref:config.adoc[]
 * xref:benchmarks.adoc[]
-** xref:benchmarks.adoc#comparisons[Comparisons]
-** xref:benchmarks.adoc#basic_operations[Add, Sub, Mul, Div]
-** xref:benchmarks.adoc#benchmark_charconv[`<charconv>`]
+** xref:benchmarks.adoc#x64_linux_benchmarks[x64 Linux]
+** xref:benchmarks.adoc#x64_windows_benchmarks[x64 Windows]
+** xref:benchmarks.adoc#m4_mac_benchmarks[ARM64 macOS]
 * xref:design.adoc[]
 * xref:reference.adoc[]
 * xref:copyright.adoc[]