update config/_default/markup.toml to allow style-sheeting paragraphs like:

#v+
A test paragraph
{.custom-style-class}
#v-

Which should result in something like:

#v+
<p class="custom-style-class">A test paragraph</p>
#v-

config/_default/markup.toml

@@ -5,6 +5,10 @@
 [goldmark.renderer]
   unsafe = true
 
+[goldmark.parser]
+[goldmark.parser.attribute]
+  block = true
+
 [highlight]
   noClasses = false