Update index.md (#36480)

* Update index.md

Added information about the scaling effect, so that the description of the effect after using “contain” is more accurate.

* Update files/en-us/web/css/object-fit/index.md

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

---------

Co-authored-by: Joshua Chen <[email protected]>
Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

files/en-us/web/css/object-fit/index.md

@@ -38,7 +38,7 @@ The `object-fit` property is specified as a single keyword chosen from the list
 ### Values
 
 - `contain`
-  - : The replaced content is scaled to maintain its {{glossary("aspect ratio")}} while fitting within the element's content box. The entire object is made to fill the box, while preserving its aspect ratio, so the object will be ["letterboxed"](<https://en.wikipedia.org/wiki/Letterboxing_(filming)>) if its aspect ratio does not match the aspect ratio of the box.
+  - : The replaced content is scaled to maintain its {{glossary("aspect ratio")}} while fitting within the element's content box. The entire object is made to fill the box, while preserving its aspect ratio, so the object will be ["letterboxed"](<https://en.wikipedia.org/wiki/Letterboxing_(filming)>) or ["pillarboxed"](https://en.wikipedia.org/wiki/Pillarbox) if its aspect ratio does not match the aspect ratio of the box.
 - `cover`
   - : The replaced content is sized to maintain its aspect ratio while filling the element's entire content box. If the object's aspect ratio does not match the aspect ratio of its box, then the object will be clipped to fit.
 - `fill`