Fixes site banner formatting for media publisher

[NejcZdovc]

Resolves brave/brave-browser#1924

UI implementation: brave/brave-ui#259
Native implementation: brave-intl/bat-native-ledger#167

Submitter Checklist:

• Submitted a ticket for my issue if one did not already exist.
• Used Github auto-closing keywords in the commit message.
• Added/updated tests for this change (for new code or code which already has tests).
• Verified that these changes build without errors on
  • Windows
  • macOS
  • Linux
• Verified that these changes pass automated tests (npm test brave_unit_tests && npm test brave_browser_tests) on
  • Windows
  • macOS
  • Linux
• Ran git rebase master (if needed).
• Ran git rebase -i to squash commits (if needed).
• Tagged reviewers and labelled the pull request as needed.
• Request a security/privacy review as needed.
• Add appropriate QA labels (QA/Yes or QA/No) to include the closed issue in milestone

Test Plan:

• enable rewards
• go to brave.com
• click on bat logo and click donate
• make sure that you see brave.com written in the banner (favicon will not work yet)

• enable rewards
• go to https://www.youtube.com/channel/UCFNTTISby1c_H-rm5Ww5rZg
• click on bat logo and click donate
• make sure that you see Brave written in the banner (favicon should work as well)

Reviewer Checklist:

• New files have MPL-2.0 license header.
• Request a security/privacy review as needed.
• Adequate test coverage exists to prevent regressions
• Verify test plan is specified in PR before merging to source

[jasonrsadler]

@NejcZdovc please rebase

[NejcZdovc]

@jasonrsadler rebased

[jasonrsadler]

master (0.59.x): 467d06e
0.58.x 147136b
0.57.x 22e7cb8

[NejcZdovc]

per @mandar-brave request adding uplift label

[kjozwiak]

@NejcZdovc approved uplift to 0.57.x after deliberating with @rebron.