Add a specific ‘.short-dl’ component

This is a component meant for definition lists with very short definitions, such
as descriptions of single-letter command-line arguments, or keyboard bindings.

src/less/include/components.less

@@ -58,6 +58,11 @@ pre.src {
   }
 }
 
+.short-dl {
+  display: grid;
+  grid-template-columns: auto auto;
+}
+
 .subtitle {
   font-size: 0.9rem;
   margin: 0;