Update error summary as per GDS Design system

[sulthan-ahmed]

The current error summary is out of date. It doesn't follow the guidelines in the GDS Design system
You must:

• add ‘Error: ’ to the beginning of the <title> so screen readers read it out as soon as possible ☑️
• show an error summary at the top of a page ☑️
• move keyboard focus to the error summary
• include the heading ‘There is a problem’ ☑️
• link to each of the answers that have validation errors ☑️
• show the same error messages next to the inputs with errors ☑️

It was agreed at least the first two items should be addressed. There is some debate about changing the focus because that changes the default behaviour of a browser

Updated: added a check to all the items done in this issue

https://design-system.service.gov.uk/components/error-summary/