DOCS: demonstrate inline highlighting

docs/user_guide/theme-elements.md

@@ -102,6 +102,24 @@ print("A code block with a caption and line numbers.")
 print("A code block with a caption and line numbers.")
 ```
 
+## Inline code
+
+When used directly, the `code` role just displays the text without syntax highlighting, as a literal. As mentioned in the [Sphinx documentation](https://www.sphinx-doc.org/en/master/usage/restructuredtext/roles.html#inline-code-highlighting) you can also enable syntax highlighting by defining a custom role. It will then use the same highligther as in the `code-block` directive.
+
+```{code-block} rst
+
+.. role:: python(code)
+   :language: python
+
+In Python you can :python:`import sphinx`.
+```
+
+```{role} python(code)
+:language: python
+```
+
+In Python you can {python}`import sphinx`.
+
 ## Code execution
 
 This theme has support for Jupyter execution libraries so that you can programmatically update your documentation with each build.