[EuiSelectable] Needs a checkbox

[bhavyarm]

https://elastic.github.io/eui/#/forms/selectable

This component needs a checkbox so that user can figure out that she needs to select it.
Right now its not obvious for the user in this example( copying saved objects between spaces)

[github-actions]

👋 Hey there. This issue hasn't had any activity for 180 days. We'll automatically close it if that trend continues for another week. If you feel this issue is still valid and needs attention please let us know with a comment.

[cchaos]

Still valid, just trying to decide if this should be default, a specific setting like (act-like-checkbox) or just a pattern using the custom renderer.

[github-actions]

👋 Hey there. This issue hasn't had any activity for 180 days. We'll automatically close it if that trend continues for another week. If you feel this issue is still valid and needs attention please let us know with a comment.

[daveyholler]

This issue is no longer valid in the current EUI theme.