feat: add additional Chess.com ad selectors and preserve message editor iframe

[jefflward]

Summary

This PR improves ad blocking coverage on Chess.com by adding additional ad element selectors and aligning script-based removal with CSS-based hiding. It also fixes an overbroad iframe rule so the TinyMCE player message editor remains visible.

Changes

Added new ad selectors

• #leaderboard-atf-ad
• #medium-rectangle-atf-ad
• #medium-rectangle-btf-ad
• .game-over-ad-sidecar-component
• .game-over-ad-component
• .medium-rectangle-ad-component

Selector consistency

• Applied the same selector additions to both the inject script and stylesheet.

TinyMCE iframe fix

• Updated iframe hiding rule from a global iframe selector to:

  iframe:not(#mce_0_ifr)

• Added a comment explaining why the TinyMCE iframe is excluded.

Why

• Chess.com serves ads in additional containers that were not covered by the previous selector set.
• Some ad elements remained visible in certain views, including game-over surfaces.
• A blanket iframe rule risked hiding legitimate product UI, including player-to-player messaging.

Impact

• Improved ad suppression across more page states.
• Preserves player-to-player message editor functionality.
• No manifest changes.
• No permission changes.

Testing

• Manually verified newly targeted ad containers are hidden.
• Confirmed the message editor iframe remains visible and usable.
• Confirmed existing selector behavior remains intact.