Add a few links to the landing page

trac-to-pelican-home.md

@@ -20,6 +20,15 @@ Pelican's [automatically-generated index](pelican-index.html) is the
 default Pelican landing page, but we had to move it aside to make room
 for this one.
 
+For the initial conversion we just use Pelican's default theme.
+There's a *lot* of room to adjust the appearance, and a lot of
+[example themes already available for Pelican](http://pelicanthemes.com/).
+
+Similarly, we don't do anything with Pelican's "category" mechanism
+because it has no direct analogue in TracWiki.  See [the Pelican
+documentation](https://docs.getpelican.com/en/stable/) for details on
+how to use the category mechanism, or how to disable it completely.
+
 Feel free to clean all of this up, this page is just a placeholder to
 make it easy to navigate the converted wiki until a human takes over.