[DOCS] Release checklist (8.1)

[jmikell821]

Checklist:

• What's New?

  • Ensure include tags are included in file for inclusion in stack-docs Highlights

• Release notes merged [DOCS] 8.1.0 Release Notes #1633
  IMPORTANT: Merge the Security release notes PR before merging the Stack docs PR. The Stack Docs PR contains links that point to anchors in the Security release notes PR and (the links) won't resolve until the Security PR is merged with main and the 8.1 release notes page is published on the docsite.

  • Ensure any breaking changes are included in stack-docs [Breaking Changes] [DOCS] Add Elastic Security breaking changes to Installation and Upgrade Guide for 8.1 stack-docs#2076

• All topics updated to reflect the new UI navigation

• All API changes merged

• D&R PRs merged and backported

• Threat Hunting PRs merged and backported

• Endpoint PRs merged and backported

• OLM PRs merged and backported

• Bug issues addressed

• Update the docs release dev issue with appropriate PR numbers

• Review and merge 8.1 prebuilt rules

• Verify that merged doc updates display correctly in main and 8.1

[jmikell821]

8.1 is released!