Update the Frontend Docs following v5.0.0 release

[romaricpascal]

What

Once GOV.UK Frontend 5.0.0 has been released to npm update our preview pull request by:

• bump the version of govuk-frontend
• update the content of "Changes to GOV.UK Frontend v5.0.0" with the final draft for "Changes to GOV.UK Frontend v5.0.0 (internal)
• update the content of "Browser support" with the final draft for "Browser support" (internal)
• replacing all links to the Frontend Docs preview (release-5-0--govuk-frontend-docs-preview.netlify.app) with links to the live site (frontend.design-system.service.gov.uk)
• replacing all links to the Design System preview (release-5-0--govuk-design-system-preview.netlify.app) with links to the live site (design-system.service.gov.uk)
• merging any other documentation PRs specific to the release

Why

So the documentation is up to date with our latest release of GOV.UK Frontend.

Done when

• [x] The preview pull request uses GOV.UK Frontend 5.0.0
• [x] The final content drafts have been used for the relevant pages
• [x] Links to the preview sites have been replaces with links to the live sites
• [x] Any outstanding content PR have been merged on the preview pull request
• [x] The preview pull request has been merged on main after review