Clarify the issues with selects

[joelanman]

Related documentation

https://design-system.service.gov.uk/components/select/

Suggestion

The guidance tells people to avoid it in most cases, we regularly get support requests to ask why - what the issues are.

Evidence (where applicable)

From support

[joelanman]

Some issues with selects are covered here:

• https://www.youtube.com/watch?v=CUkMCQR4TpY
• https://designnotes.blog.gov.uk/2013/12/05/asking-for-a-date-of-birth/
• https://github.com/alphagov/govuk-design-system-backlog/issues/60 (note the 3D ios implementation)