Add intersphinx example

Author: benjaoming

docs/_toc.yml

@@ -8,3 +8,4 @@ chapters:
 - file: notebooks
 - file: markdown-notebooks
 - file: sphinx-hoverxref
+- file: intersphinx

docs/intersphinx.md

@@ -0,0 +1,28 @@
+# Intersphinx
+
+Behind the built-in Sphinx extension `intersphinx` is a powerful tool to reference sections in other Sphinx and Jupyter Book documentation projects.
+
+You can configure mappings to external Sphinx projects in your Jupyter Book configuration, the `_config.yml` file. In this example project, we have configured `ebp` to reference `https://executablebooks.org/en/latest/`. In the following code examples, we refer to the configured `ebp` mapping and link directly to a section called `tools`.
+
+```{tab} MyST (Markdown)
+
+```{example}
+We can link to pages in other documentation projects.
+This is a link to the
+[Executable Book project's list of tools they build](ebp:tools)
+```
+
+
+```{tab} reStructuredText
+
+```{example}
+
+```{eval-rst}
+We can link to pages in other documentation projects.
+This is a link to the
+:doc:`Executable Book project's list of tools they build <ebp:tools>`
+```
+
+```{note}
+In the above `reStructuredText` example, we use `{eval-rst}` to write reST inside a `.md` file (i.e. the one you are reading now). You only need to use this directive if you are writing reST code in a `.md` file.
+```