fix(css): The content-visibility: auto marks a containing block

files/en-us/web/css/containing_block/index.md

@@ -38,6 +38,7 @@ The process for identifying the containing block depends entirely on the value o
    2. A {{cssxref("contain")}} value of `layout`, `paint`, `strict` or `content` (e.g. `contain: paint;`).
    3. A {{cssxref("container-type")}} value other than `normal`.
    4. A {{cssxref("will-change")}} value containing a property for which a non-initial value would form a containing block (e.g. `filter` or `transform`).
+   5. A {{cssxref("content-visibility")}} value of `auto`.
 
 > [!NOTE]
 > The containing block in which the root element ({{HTMLElement("html")}}) resides is a rectangle called the **initial containing block**. It has the dimensions of the viewport (for continuous media) or the page area (for paged media).