add TOC to dependencies guide

support/doc/dependencies.md

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 # Dependencies
 
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+- [Debian / Ubuntu and derivatives](#debian--ubuntu-and-derivatives)
+- [Arch Linux](#arch-linux)
+- [CentOS 7](#centos-7)
+- [Fedora](#fedora)
+- [FreeBSD](#freebsd)
+- [macOS](#macos)
+- [Gentoo](#gentoo)
+- [Other distributions](#other-distributions)
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 ## Debian / Ubuntu and derivatives
   1. On a fresh Debian/Ubuntu, as root user, install basic utility programs needed for the installation