Add link hover background reference.

[skip ci]

docs/styles/links/link_hover_background.md

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+# Link-hover-background
+
+The `link-hover-background` sets the background color of the link.
+
+!!! note
+
+    `link-hover-background` only applies to "action links" as described in the [actions guide](../../guide/actions.md#links) and not to regular hyperlinks.
+
+## Syntax
+
+```sass
+link-hover-background: <COLOR> <PERCENTAGE>;
+```
+
+--8<-- "docs/styles/snippets/color_css_syntax.md"
+
+--8<-- "docs/styles/snippets/percentage_syntax.md"
+
+## Example
+
+The example below shows some links that have their background colour changed when the mouse moves over it and it shows that there is a default color for `link-hover-background`.
+
+It also shows that `link-hover-background` does not affect hyperlinks.
+
+=== "Output"
+
+    ![](./demos/link_hover_background_demo.gif)
+
+    !!! note
+
+        The GIF has reduced quality to make it easier to load in the documentation.
+        Try running the example yourself with `textual run docs/examples/styles/link_hover_background.py`.
+
+=== "link_hover_background.py"
+
+    ```py hl_lines="8-9 12-13 16-17 20-21"
+    --8<-- "docs/examples/styles/link_hover_background.py"
+    ```
+
+    1. This label has an hyperlink so it won't be affected by the `link-hover-background` rule.
+    2. This label has an "action link" that can be styled with `link-hover-background`.
+    3. This label has an "action link" that can be styled with `link-hover-background`.
+    4. This label has an "action link" that can be styled with `link-hover-background`.
+
+=== "link_hover_background.css"
+
+    ```css hl_lines="2 6 10"
+    --8<-- "docs/examples/styles/link_hover_background.css"
+    ```
+
+    1. This will only affect one of the labels because action links are the only links that this rule affects.
+    2. The default behavior for links on hover is to change to a different background color, so we don't need to change anything if all we want is to add emphasis to the link under the mouse.
+
+## CSS
+
+```css
+link-hover-background: red 70%;
+link-hover-background: $accent;
+```
+
+## Python
+
+```py
+widget.styles.link_hover_background = "red 70%"
+widget.styles.link_hover_background = "$accent"
+
+# You can also use a `Color` object directly:
+widget.styles.link_hover_background = Color(100, 30, 173)
+```