Add custom shortcut instructions to terminator.md

[andcscott]

Greetings, this PR adds instructions for setting custom keybinds to terminator.md as suggested by @sspencerwire in #2441. Thank you!

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)

[github-actions]

Test results for 48c6a1f:

Number of broken URLs: 6

URL,RESULT,FILENAME
 http://rocky.reloumirrors.net/9.4/extras/x86_64/os/repodata/7d78a729-8e9a-4066-96d4-ab8ed8f06ee8-FILELISTS.xml.gz,failed,books/web_services/053-load-balancer-proxies-squid.md
 http://miroir.univ-lorraine.fr/rocky/9.4/AppStream/x86_64/os/repodata/1af312c9-7139-43ed-8761-90ba3cd55461-UPDATEINFO.xml.gz,failed,books/web_services/053-load-balancer-proxies-squid.md
 http://www.example.org/foo.txt,failed,books/web_services/052-load-balancer-proxies-varnish.md
 http://0.0.0.0:61208/,failed,guides/network/glances_network_monitoring.md
 https://www.qyecst.cn,failed,guides/contribute/README.md
 https://azuremarketplace.microsoft.com/en-us/marketplace/apps/resf.rockylinux-aarch64,failed,guides/cloud/migration-to-new-azure-images.md

[Grammaresque]

Issue #2417. thanks for your contributions in October, Andrew! I hope you find places to stick around and contribute more. We are glad to have you as part of the community!

[sspencerwire]

Thanks @andcscott! Much appreciated!