Update SKILL.md for handling multpile issues

[wadepickett]

AspNetCore.Docs/.github/skills/whats-new-include-content-rules/SKILL.md

Line 157 in 55aba25

* The very first line of the PR description must be `Fixes dotnet/AspNetCore.Docs#{ISSUE NUMBER}` (where `{ISSUE NUMBER}` is the number of the issue this PR addresses), followed by a blank line before any other content.

This folllowing section needs to also address the situation where the PR fixes more then one Issue or is related to other issues:

PR description requirements

• The very first line of the PR description must be Fixes dotnet/AspNetCore.Docs#{ISSUE NUMBER} (where {ISSUE NUMBER} is the number of the issue this PR addresses), followed by a blank line before any other content.
• Example:

---

Associated WorkItem - 580697