Add content to implementation tab for Banner

#### Dismiss

Users are able to permanently dismiss banners by default. Banners may also be dismissed temporarily, depending on the use case.

##### Permanent dismissal

The dismiss action is always represented by the `Close` icon and anchored to the top right of the banner.

Banner dismissal should work as follows:
* Banner dismissal must be associated with the user in the system database. Dismissal must persist, even across version upgrades and clients.
* Banners do not reappear by default. In rare circumstances, you may present the banner again to a user after some time has passed.
* Banners should only be shown to users who are logged in.

**Implementation Notes:**
* The dismissal of the banner is achieved using the `UserCallout` model on the backend and the `PersistentUserCallout` JS file on the frontend. If both parameters are implemented correctly, the banner will adhere to the dismissal guidelines above.

##### Temporary dismissal
To introduce temporary dismissal, include a secondary or tertiary button placed alongside the primary action button. Follow the [button](/components/button#alignment-and-order) alignment and order guidelines.

Temporary dismissals should work as follows: 
* Banners dismissed temporarily will reappear after **7 days**.
* After a banner is dismissed temporarily, use a [toast](/components/toast) message to let the user know they will see the banner again in 7 days.