chore(adaptiveness): mention subtitle prop (#1823)

* chore(adaptiveness): mention subtitle prop

Related to https://github.com/telerik/blazor/issues/8256

* Update common-features/adaptive-rendering.md

Co-authored-by: Yordan <60105689+yordan-mitev@users.noreply.github.com>

---------

Co-authored-by: Nadezhda Tacheva <73842592+ntacheva@users.noreply.github.com>
Co-authored-by: Yordan <60105689+yordan-mitev@users.noreply.github.com>

common-features/adaptive-rendering.md

@@ -40,7 +40,7 @@ To enable the adaptive rendering use the `AdaptiveMode` parameter. It takes a me
 * `None` (default)
 * `Auto`
 
-Optionally, you may set the `Title` parameter to provide custom header text for the popup on small and medium devices.
+Optionally, you may set the `Title` and `Subtitle` parameters to provide custom header and subtitle text for the popup on small and medium devices.
 
 >caption Enable the adaptive rendering