Add better support for tabs

Some pages break without actual tab support, such as
https://breezewiki.com/ben10/wiki/Ultimatrix_(Original)#Modes

This change aims to work with old browsers (such as Firefox for Android 68)
and browsers with Javascript disabled (by showing all tab contents and hiding
the tab bar, i.e. how tabs work before this change).

static/main.css

@@ -202,11 +202,11 @@ figcaption, .lightbox-caption, .thumbcaption {
     padding: 0;
 }
 
-/* show tabs always */
-.wds-tabs__wrapper {
+/* show tabs if tabs.js isn't loaded */
+.bw-tabs-nojs .wds-tabs__wrapper {
     display: none;
 }
-.wds-tab__content {
+.bw-tabs-nojs .wds-tab__content {
     display: block;
 }