Implement keyboard events for links with a role of button

[robinwhittleton]

govuk_frontend_toolkit 4.15.0 will include a shim for fixing keyboard events on links with a role of button. In the frontend meeting it was decided that we’d implement this in static initially to test, and then decide whether to migrate it over to govuk_template. @cfq also requested that this usage was recorded in analytics too so that we can see how many people this affects.

[gemmaleigh]

For further context, here's the discussion on GOV.UK elements, which led to the creation of the shim to allow anchors with role="button" to be 'clicked' via the space key. (thanks to @paulmsmith).

[gemmaleigh]

The govuk_frontend_toolkit has now been updated to 4.16.1, so this work can go ahead.

[gemmaleigh]

Here's how it's used in govuk_elements:

  // Use GOV.UK shim-links-with-button-role.js to trigger a link styled to look like a button,
  // with role="button" when the space key is pressed.
  GOVUK.shimLinksWithButtonRole.init()

[NickColley]

Just realised that this should be 'keyDown' not 'keyUp' since the page currently scrolls and then follows the link..