Allow the user to open the Crate Page from the crate dropdown

This fixes a regression added by the keyboard-accessible JavaScript menus,
where clicking the link opened the menu instead of the linked page.
It checks if the link points somewhere, and lets it behave normally if it does.

Also adds keyboard handling for the space key, so you can still get to the menu.

Author: notriddle

templates/menu.js

@@ -39,6 +39,9 @@
         backdrop.style.display = "block";
     }
     function menuOnClick(e) {
+        if (this.getAttribute("href") != "#") {
+            return;
+        }
         if (this.parentNode === currentMenu) {
             closeMenu();
         } else {
@@ -123,6 +126,7 @@
                 case "enter":
                 case "return":
                 case "space":
+                case " ":
                     // enter, return, and space have the default browser behavior,
                     // but they also close the menu
                     // this behavior is identical between both the WAI example, and GitHub's
@@ -155,6 +159,17 @@
                 e.preventDefault();
                 e.stopPropagation();
             }
+        } else if (e.target.parentNode.className && e.target.parentNode.className.indexOf("pure-menu-has-children") !== -1) {
+            switch (e.key.toLowerCase()) {
+                case "arrowdown":
+                case "down":
+                case "space":
+                case " ":
+                    openMenu(e.target.parentNode);
+                    e.preventDefault();
+                    e.stopPropagation();
+                    break;
+            }
         }
     };
     var menus = Array.prototype.slice.call(document.querySelectorAll(".pure-menu-has-children"));