Support the dark theme on the rewards page (dark mode)

[dizeeee]

This is a pretty simple problem, the colors setting that can be found in the appearance section of the menu does not seem to apply to the rewards page. The styling for the rewards page needs to be updated to support it.

[NejcZdovc]

+1 from #8926

[eljuno]

Duplicate of #2822?

[NejcZdovc]

let's keep it. Added link to this issue in #2822

[anji5h]

It's 2021 and still, the issue is not fixed.

[bsclifton]

Hi folks

We are working on a new "2.0" interface for Rewards; you can track those issues with the rewards-ui-2.0 label. I've added this so we don't forget to include it in the scope of the work

[Rybec]

Halfway through 2022, and it's still a problem.

[Miyayes]

We will be moving to a whole new Rewards interface in Rewards 3.0 (a "cards model" that unifies with the Brave Wallet interface). There, we will have a dark version of the UI, since the Brave Wallet UI in general always has a light/dark theme. Since that is on the horizon, I will close this particular issue as "wontfix", since I will take it as referring to the classic Rewards settings page.