Retire vf-explainer component

[nikiforosk]

The implementation of the vf-explainer component hasn't been completed.

The basic use case for providing details is supported by vf-details. For highlighting explanations we suggested that the Comms team uses vf-card.

• [ ] Justification text: This component hasn't been implemented. The basic use case for providing details is supported by vf-details. For highlighting explanations we suggested that the Comms team uses vf-card.
• [ ] Use the red banner and the Deprecated badge as we do for vf-banner.
• [ ] Remove from the list of Elements on the Components page and the VF megamenu.
• [ ] Read the instructions on Deprecating components

[sandykadam]

As of now, this component is not used anywhere in any website. This was just an experimental component added.

[bhushan-ebi]

PR - https://github.com/visual-framework/vf-core/pull/2040