* Fix template and preview overflowing container
* Fix extra whitespace around "documentation" link
* Increase minimal height of the template input field
"Note format" section in "Export" tab is technically a table and is
announced as such by screen readers, which is misleading.
It also opens a menulist when a checkbox is clicked, which is
not an expected behavior and can shift focus.
This refactors the "Note format" section to be a vbox container
with <checkbox>es and labels, which is more correct semantically and
does not confuse screen readers. In addition, when a chekbox is
clicked, dispatch a "change" event instead of unnecessarily open
up a menu.
