TINYDOC-3560: TinyMCE 8.8.1 Release Documentation.

[kemister85]

Ticket: TINYDOC-3560

Site: Staging branch

Changes:

• Added the 8.8.1 release notes page (modules/ROOT/pages/8.8.1-release-notes.adoc) scaffolded from the release-notes template.
• Added the 8.8.1 entry to modules/ROOT/nav.adoc under Release information.
• Added the 8.8.1 cell to the release notes index (modules/ROOT/pages/release-notes.adoc).
• Added the 8.8.1 changelog entry (modules/ROOT/pages/changelog.adoc).

Foundation scaffold for the {productname} 8.8.1 release. The concrete release date is populated on the feature/container branch (feature/8.8.1/TINYDOC-3560).

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Pre-checks:

• Branch is correctly prefixed:

• Feature: feature/<version>/DOC-XXXX (e.g., feature/8.0.0/DOC-1234)

• Hotfix: hotfix/<version>/DOC-XXXX (e.g., hotfix/8.0.0/DOC-1234)

• EPIC: release/<ver> (e.g., release/8.0.0 for major releases)

• modules/ROOT/nav.adoc has been updated (if applicable).

• Files have been included where required (if applicable).

• Files removed have been deleted, not just excluded from the build (if applicable).

• Files added for New product features include a release note entry.

• Major or minor version changes have updated the supported-versions.adoc table.

• Build passes without console errors, warnings, or issues.

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Review:

• Documentation Team Lead has reviewed.