H5: Add an entry to the table of contents

exercises/h5.md

@@ -25,6 +25,8 @@ This exercise is a part of [Linux servers (ICT4TN021, spring 2018) // Linux-palv
 
 - [d) **SSH auto-login** Automate SSH login with public key method](https://github.com/Fincer/linux_server_setup/blob/master/exercises/h5.md#d-automate-ssh-login-with-public-key-method)
 
+    - [EXTRA: Modifying welcome banner](https://github.com/Fincer/linux_server_setup/blob/master/exercises/h5.md#extra-modifying-welcome-banner)
+
 - [e) **Analysis of server processes** Install, configure and start sysstat. Use sar command to confirm whether the sysstat package services have been enabled (for instance, log entry "Linux reboot..." exists). Run sysstat a day or two. Afterwards, check computer workload history with sysstat commands sar, iostat, pidstat etc. Analyze the results, i.e. explain the results in detail.](https://github.com/Fincer/linux_server_setup/blob/master/exercises/h5.md#e-install-configure-and-start-sysstat-use-sar-command-to-confirm-whether-the-sysstat-package-services-have-been-enabled-for-instance-log-entry-linux-reboot-exists-run-sysstat-a-day-or-two-afterwards-check-computer-workload-history-with-sysstat-commands-sar-iostat-pidstat-etc-analyze-the-results-ie-explain-the-results-in-detail)
 
     - [SAR - network statistics, IPv4 traffic](https://github.com/Fincer/linux_server_setup/blob/master/exercises/h5.md#sar---network-statistics-ipv4-traffic)