Update index.md

[SergeCroise]

• Link to newer release notes (8_7) as example for long document.
• Punctuation.

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 0a85186:

Number of broken URLs: 2

URL,RESULT,FILENAME
 https://mirror2.sandyriver.net/pub/rocky/8.6/PowerTools/x86_64/os/,failed,books/admin_guide/13-softwares.md
 https://ersei.saggis.com/,failed,guides/contribute/README.md

[sspencerwire]

Thanks @SergeCrois! This looks good.