Prepare release notes and comms for v5.9.0

[calvin-lau-sig7]

Release comms doc

Release notes to be created in release notes folder

• Changelog draft for File upload

What

Prepare:

• Changelog and release notes
• Release comms, including email and Slack messages

Headlines:

• improved File upload component
• deprecating the service name and navigation links in the GOV.UK header
• use Service navigation instead

Why

We want to support service teams to use the new component, and migrate to using the Service navigation

Who needs to work on this

Content designer, technical writer, v5.9 lead (@domoscargin)

Who needs to review this

Involved squads

Done when

• changelog entries gathered
• changelog reviewed by technical writer with developers
• changelog 2i review
• release notes created from changelog
• release comms drafted for various platforms
• release comms reviewed by involved squads and finalised
• comms platforms prepared ahead of release