Showing the mesh contents in the readme

[jon-proximafusion]

I would be keen to somehow highlight the tags and how they appear in the mesh in the readme.

Perhaps after this line in the readme

The resulting .msh file should have three physical groups named for tags in it. The in_contact group should include the faces from both the shell and the insert.

We could insert a snippet of a mesh that has the tags highlighted.

perhaps and expandable snippet like this, which I've had working in readme.md files on github before, looks like it doesn't work in issues

<details>
  <summary><b>Expand</b> - See the resulting mesh?</summary>
    <pre><code class="language-html">
   contents of the mesh here with highlighted tags
    </code></pre>
</details>

I think this would clearly show

This is something I can take on when I get a few mins space, just making an issue so i don't forget