TINYDOC-3528: TinyMCE 8.8.0 Release Documentation.

[kemister85]

Ticket: TINYDOC-3528

Site: Staging branch

Changes:

• Scaffolded the {productname} 8.8.0 release notes foundation from the release-notes template.
• Added modules/ROOT/pages/8.8.0-release-notes.adoc with all standard sections (author-time placeholders retained for content to be filled in).
• Added the 8.8.0 navigation block to modules/ROOT/nav.adoc.
• Added the 8.8.0 entry to the release notes index (modules/ROOT/pages/release-notes.adoc).
• Added the 8.8.0 changelog heading to modules/ROOT/pages/changelog.adoc.
• Added the 8.8 row to modules/ROOT/partials/misc/supported-versions.adoc.

This is the release foundation (EPIC) branch for 8.8.0. Release content and the confirmed release date are added on child feature branches.

---

Pre-checks:

• Branch is correctly prefixed: release/8.8.0 (EPIC)
• modules/ROOT/nav.adoc has been updated.
• Files have been included where required.
• Files removed have been deleted, not just excluded from the build (n/a).
• Files added for release documentation 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.

---

Review:

• Documentation Team Lead has reviewed.