Proposition : enhancement of tag sub/sup

Proposition helps to avoid bad line-height rendering caused by sub and sup tags. (use these tags on big blocks of texts with and without the fix to see the difference)

In french : la proposition aide à éviter des interlignages disgracieux causés par les balises sup et sub. ;)

css/knacss.css

@@ -138,6 +138,18 @@ mark {
 	padding:2px 4px;
 	background: #ff0;
 }
+/* avoid bad line-height */
+sup,
+sub {
+  vertical-align: 0;
+  position: relative;
+}
+sup {
+  bottom: 1ex;
+}
+sub {
+  top: .5ex;
+}
 
 table { margin-bottom: 1.5em; }