Add margin only to the top of a <p> following a <p>

This way if something other than a paragraph follows the paragraph it won't
automatically and unnecessarily be pushed down.

src/scss/include/_common.scss

@@ -109,7 +109,7 @@ pre {
 
 p { margin: 0; }
 
-p + p { margin: 1rem 0; }
+p + p { margin: 1rem 0 0 0; }
 
 .footdef {
   display: grid;