Add more input types, fix lowercase nodeName, support shift-backspace

go-back-with-backspace/content_script.js

-// Listen for the backspace key and go back if not in an editable field.
+// Listen for shift-backspace or unmodified backspace and navigate if not in
+// an editable field.
 document.addEventListener('keydown', function(e) {
-  if (e.which === 8 &&  // backspace key code
+  if (e.key === 'Backspace' &&
+      !e.altKey &&
+      !e.ctrlKey &&
+      !e.metaKey &&
       !isEditable(e.path)) {
-    window.history.back();
+    e.shiftKey ? window.history.forward(): window.history.back();
     e.preventDefault();
   }
 });