treewide: convert options with lists to Markdown

`nix-doc-munge` can't handle these, which is understandable as I can
barely handle them either. There are a few infelicities here: the
current processor can't handle multiple terms to one description in
a description list so they get comma-separated in one case, and one
case that should ideally render as a `<figure>` with a `<figcaption>`
in HTML is reduced to a paragraph with some `<strong>` text. (Which, in
fairness, is how it rendered in practice with the DocBook anyway.) The
docs generator has since been updated to handle figures, but we can't
use it until moving off DocBook output.

modules/programs/astroid.nix

@@ -79,15 +79,20 @@ in {
           };
         example =
           "nvim-qt -- -c 'set ft=mail' '+set fileencoding=utf-8' '+set ff=unix' '+set enc=utf-8' '+set fo+=w' %1";
-        description = ''
-          You can use <code>%1</code>, <code>%2</code>, and
-          <code>%3</code> to refer respectively to:
-          <orderedlist numeration="arabic">
-            <listitem><para>file name</para></listitem>
-            <listitem><para>server name</para></listitem>
-            <listitem><para>socket ID</para></listitem>
-          </orderedlist>
-          See <link xlink:href='https://github.com/astroidmail/astroid/wiki/Customizing-editor' />.
+        description = lib.mdDoc ''
+          You can use the following variables:
+
+          `%1`
+          : file name
+
+          `%2`
+          : server name
+
+          `%3`
+          : socket ID
+
+          See [Customizing editor](https://github.com/astroidmail/astroid/wiki/Customizing-editor)
+          on the Astroid wiki.
         '';
       };