Add text-decoration-trim experimental feature entry (#41665)

* Add text-decoration-trim experimental feature entry

* Add paragraph to Fx145 rel notes experimental section

* Update files/en-us/mozilla/firefox/releases/145/index.md

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

---------

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

Author: 3 people

files/en-us/mozilla/firefox/experimental_features/index.md

@@ -350,6 +350,20 @@ The {{CSSXRef(":heading")}} pseudo-class allows you to style all [heading elemen
 - `layout.css.heading-selector.enabled`
   - : Set to `true` to enable.
 
+### `text-decoration-trim`
+
+The CSS `text-decoration-trim` property allows you to specify {{cssxref("text-decoration")}} start and end offsets to shorten, lengthen, or shift the position of text decorations with respect to the text ([Firefox bug 1979915](https://bugzil.la/1979915)).
+
+| Release channel   | Version added | Enabled by default? |
+| ----------------- | ------------- | ------------------- |
+| Nightly           | 145           | No                  |
+| Developer Edition | 145           | No                  |
+| Beta              | 145           | No                  |
+| Release           | 145           | No                  |
+
+- `layout.css.text-decoration-trim.enabled`
+  - : Set to `true` to enable.
+
 ## SVG
 
 **No experimental features in this release cycle.**

files/en-us/mozilla/firefox/releases/145/index.md

@@ -112,3 +112,8 @@ You can find more such features on the [Experimental features](/en-US/docs/Mozil
   Nightly builds now support [CSS anchor positioning](/en-US/docs/Web/CSS/CSS_anchor_positioning) by default, which allows you to tether elements together.
   The anchor-positioned elements can then have their size and position set relative to the size and location of the anchor elements to which they are bound.
   (General: [Firefox bug 1988224](https://bugzil.la/1988224), `position-area`: [Firefox bug 1924086](https://bugzil.la/1924086)).
+
+- **text-decoration-trim**: `layout.css.text-decoration-trim.enabled`
+
+  The CSS `text-decoration-trim` property is supported but currently disabled by default.
+  It allows you to specify {{cssxref("text-decoration")}} start and end offsets to shorten, lengthen, or shift the position of text decorations with respect to the text ([Firefox bug 1979915](https://bugzil.la/1979915)).