Create release notes for package lock-related release of GOV.UK Prototype Kit

[EoinShaughnessy]

What

Create release notes for package lock-related release of GOV.UK Prototype Kit.

Why

We need to tell users about a fix we're introducing that will hopefully clear up the security issues we've been asking them to fix recently.

We also need to emphasise to users:

• that they should upgrade to this new version of the Kit
• why this upgrade is so important for them to make
• that we'll help them if they have any difficulty upgrading

Who needs to work on this

Developers, technical writer

Who needs to review this

Two technical writers (one for pre-i, one for 2i)

Done when

• [x] We decide whether this is a 'breaking' or 'feature' release
• [x] Release notes drafted
• [x] Draft passes pre-i
• [x] Draft passes 2i
• [x] Draft published

[EoinShaughnessy]

@joelanman @lfdebrux Here's the first pass at release notes: https://docs.google.com/document/d/1eIGu4esdk9u8rQh1DS7XL6MSTeyqJrViecwEwZy4yFU/edit

Please advise on tone and let me know what else we might need to add (like details about the lockfileversions). :)

[EoinShaughnessy]

@joelanman Do we need to link a PR to this issue?

[domoscargin]

I've linked the V11 release PR to this issue as that includes the CHANGELOG updates.

[EoinShaughnessy]

@domoscargin Nice! Thank you.