Update the CONTRIBUTING.md guide with GPG key verification instructions

[sianford]

Current behaviour

There is no instruction in the CONTRIBUTING.MD guide to set up GPG key verification.

Also, the getting-started link to the getting-started.stories.mdx from the CONTRIBUTING.MD guide does not work.

Expected behaviour

If a dev already has their environment set up and just needs to add Carbon to their project they will likely not consult the dev-environment-setup.md and miss the instruction to add GPG key verification. This should be added to the CONTRIBUTING.MD guide, or at least direct the reader to that section in the dev-environment-setup.md doc.

The link text getting-started should link to the correct getting-started.stories.mdx doc.

CodeSandbox or Storybook URL

https://github.com/Sage/carbon/blob/master/CONTRIBUTING.md

JIRA Ticket (Sage Only)

FE-5358

Suggested Solution

Update the docs

Carbon Version

110.3.0

Design Tokens Version

No response

What browsers are you seeing the problem on?

Firefox, Chrome, Safari, Microsoft Edge

What Operating System are you seeing the problem on?

MacOS

Anything else we should know?

No response

Confidentiality

• [X] I confirm there is no confidential or commercially sensitive information included.

[nicktitchmarsh]

FE-5358