Add a bit of docs

docs/scripts/linenumber.js

@@ -0,0 +1,25 @@
+/*global document */
+(function() {
+    var source = document.getElementsByClassName('prettyprint source linenums');
+    var i = 0;
+    var lineNumber = 0;
+    var lineId;
+    var lines;
+    var totalLines;
+    var anchorHash;
+
+    if (source && source[0]) {
+        anchorHash = document.location.hash.substring(1);
+        lines = source[0].getElementsByTagName('li');
+        totalLines = lines.length;
+
+        for (; i < totalLines; i++) {
+            lineNumber++;
+            lineId = 'line' + lineNumber;
+            lines[i].id = lineId;
+            if (lineId === anchorHash) {
+                lines[i].className += ' selected';
+            }
+        }
+    }
+})();