Add rules based on contents, not ids

[Benjamin-Loison]

Prerequisites

• [X] I verified that this is not a filter list issue. Report any issues with filter lists or broken website functionality in the uAssets issue tracker.
• [X] This is NOT an issue with YouTube, Facebook or Twitch.
• [X] This is not a support issue or a question. For support, questions, or help, visit /r/uBlockOrigin.
• [X] I performed a cursory search of the issue tracker to avoid opening a duplicate issue.
• [X] The issue is not present after disabling uBO in the browser.
• [X] I checked the documentation to understand that the issue I am reporting is not normal behavior.

I tried to reproduce the issue when...

• [X] uBO is the only extension.
• [X] uBO uses default lists and settings.
• [X] using a new, unmodified browser profile.

Description

See Improve_websites_thanks_to_open_source/issues/638.

I am looking for some guarantee that I will not hide a potentially important different message.

A specific URL where the issue occurs.

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Steps to Reproduce

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Expected behavior

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Actual behavior

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uBO version

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Browser name and version

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Operating System and version

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