Add "Blur" and "Highlight" Picker Mode Feature for Elements

### Issue Details

If possible, a "blur" feature that allows sensitive content on a webpage to be blurred with a single click, and a "highlight" feature that adds a red border around elements for emphasis — both temporarily enabled through a button/shortcut in the new element picker mode. These features would make it easier to take screenshots (and possibly videos) without exposing sensitive content. This eliminates the need for third-party editing tools and simplifies the process.

### Proposed solution

For example:

* https://example.com/
* ```adb
example.com#$#h1 { filter: blur(20px) }
example.com#$#p { border: 1px solid red; }
```

### Alternative solution

If, for some technical reasons, it's not possible to add these features directly into the AdGuard Adblocker extension, then maybe you could consider creating a separate AdGuard helper extension—just like AdGuard Extra. It could work similarly to the Screenity extension (`https://screenity.io/en/`), but more advanced. For example, it could offer features like easy screenshot capture, screen recording, permanent blur, selective element highlighting, and so on—basically, all the features that would be useful for reporting issues.