Gemstones: add iftop entry

[neelchauhan]

Author checklist (Completed by original Author)

• Good fit for the Rocky Linux project? Title and Author Metatags inserted ?
• If applicable, steps and instructions have been tested to work
• Initial self-review to fix basic typos and grammar completed

Rocky Documentation checklist (Completed by Rocky team)

• 1st Pass (Document is good fit for project and author checklist completed)
• 2nd Pass (Technical Review - check for technical correctness)
• 3rd Pass (Detailed Editorial Review and Peer Review)
• Final approval (Final Review)

[neelchauhan]

Hi all, I have committed the suggestions made.

[github-actions]

Test results for 6f799a5:

Number of broken URLs: 3

URL,RESULT,FILENAME
 https://www.linode.com/docs/guides/beginners-guide-to-lxd-reverse-proxy,failed,guides/containers/lxd_web_servers.md
 https://linoxide.com/install-cockpit-on-almalinux-or-rocky-linux/,failed,guides/security/firewalld-beginners.md
 https://oktools.net/regex,failed,books/sed_awk_grep/1_regular_expressions_vs_wildcards.md