Design Request: Underline Clickable Text Of Expand/Collapse Component

[stingrayfunk]

Problem

For expand/collapse components (details/summary tags), currently the clickable blue text is not underlined.

Proposed Solution

Either:

• Make a design decision as to whether these clickable expand/collapse links should be underlined.
• Provide an optional modifier so that designers can underline the clickable text in their service, though this makes the component inconsistent across the services and is not recommended.

[gordonmcmullan]

Closing as Assets-Frontend v3/4 will adopt the styling used in govuk-elements for these