AG-27455 update the :has() pseudo-class section

AdguardTeam/AdguardBrowserExtension#2587

Author: slvvko

docs/general/ad-filtering/create-own-filters.md

@@ -3595,22 +3595,31 @@ Draft CSS 4.0 specification describes the [`:has()` pseudo-class](https://www.w3
 
 Rules with the `:has()` pseudo-class must use the [native implementation of `:has()`][native-has]
 if they use the `##` rule marker and if it is possible, i.e., there are no other extended CSS selectors inside.
-If it is not supported by the product, ExtendedCss implementation will be used even for rules with the `##` marker.
+If it is not supported by the product (or by the browser in case of AdGuard Browser Extension),
+ExtendedCss implementation will be used automatically as a fallback,
+even for rules with the `##` marker.
 
-Currently, not all AdGuard products support the native implementation of `:has()` yet:
+AdGuard products support the native implementation of `:has()`:
 
-- AdGuard for Windows, AdGuard for Mac, AdGuard for Android, and AdGuard for Linux **do support** it with [CoreLibs] v1.12 or later.
-- AdGuard for iOS and AdGuard for Safari **do support** it with [SafariConverterLib](#safari-converter-lib) v2.0.39 and [Safari browser v16.4][safari-16.4].
-- AdGuard Browser Extension **does not support** it yet, but it is [planned][AdguardBrowserExtension#2587].
+- AdGuard for Windows, AdGuard for Mac, AdGuard for Android, and AdGuard for Linux **support** it with [CoreLibs] v1.12 or later.
+- AdGuard for iOS and AdGuard for Safari **support** it with [SafariConverterLib](#safari-converter-lib) v2.0.39 and [Safari browser v16.4][safari-16.4] or later.
+- AdGuard Browser Extension **supports** it in v5.3 or later:
+    - **Manifest V3** (Chromium-based): always uses native `:has()` by default.
+    - **Manifest V2**: Detects native `:has()` support using `CSS.supports()` and falls back to ExtendedCss if the browser doesn’t support it natively.
+- All other AdGuard products **do not support** it.
 
-To force the ExtendedCss implementation of `:has()` to be used, use the `#?#` or `#$?#` rule markers explicitly,
+To force the ExtendedCss implementation of `:has()` to be used (regardless of native support),
+use the `#?#` or `#$?#` rule markers explicitly,
 e.g., `example.com#?#p:has(> a)` or `example.com#$?#div:has(> span) { display: none !important; }`.
 
+And since the `:has()` pseudo-class cannot be nested within another `:has()`
+in native implementation, e.g. `div:has(p:has(a))`,
+it is always treated as extended in AdGuard Browser Extension.
+
 :::
 
 [native-has]: https://developer.mozilla.org/docs/Web/CSS/:has
 [safari-16.4]: https://www.webkit.org/blog/13966/webkit-features-in-safari-16-4/
-[AdguardBrowserExtension#2587]: https://github.com/AdguardTeam/AdguardBrowserExtension/issues/2587
 
 **Compatibility with other pseudo-classes**