[Brave News]: Add new opt-in peeking card for Desktop

[LorenzoMinto]

Description

An opt-in peeking card (following the behaviour of our post opt-in peeking cards) explaining the benefits of enabling News would greatly help discovery. Currently the only way to find Brave News is to scroll down in the NTP.

Design: https://www.figma.com/design/wpjvatVQQvOtC96WaPCw86/%F0%9F%93%B0-Brave-News?node-id=5774-7923&t=CgJatcEZtbMgMHbX-4

Note: this messages are hardcoded in the client and will not be fetched from any service.

Proposed behaviours:

• Turning Brave News on from the peeking card will take the user straight to the feed
• We should display the peeking card with a backoff policy. Furthermore, the current design includes a way to dismiss the nudge for good.
• We should have a small set of diverse messaging and try them cyclically when nudging the user again (personalization vs privacy vs rss feeds vs top news).

[petemill]

Just to be clear - the peeking card will not show any news content since that content won't be fetched until the user opts-in. But it will show a static message (or one of a few hard-coded choices).

[LorenzoMinto]

Updated the screenshot to make this more apparent 👍