Make AdGuard versions of no-doomscroll filter lists

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Description

Currently, no-doomscroll lists only work with Zen and uBlock Origin. We need to add support for AdGuard.

The issue is the :matches-path pseudo-selector, which AdGuard's extended CSS implementation doesn't support. AdGuard uses the $path modifier instead: AdguardTeam/CoreLibs#124 (comment)

I've attempted to rewrite the rules using $path for AdGuard without success. See these commits: 8244e61, 2db7b2b. The specific problem is selecting only the index page of a website, which we achieve using :matches-path(/^\/$/).

Acceptance criteria

• AdGuard lists successfully replicate the behavior of :matches-path(/^\/$/)
• New filter lists are placed alongside existing ones with the naming pattern main-ag.txt (see 8244e61 for structure), including the index list

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Good first issue

👋 This is marked as a good first issue. External contributions are welcome.