Changes the link's destination so it points to the previous URL.
If no previous URL is known, the link will not be changed.
Note
Clicking an a[up-back] will not call history.back().
Instead the link's [up-href] attribute will be set to the actual, previous URL.
Example
This link …
<a href="/default" up-back>
Go back
</a>
… will be transformed to:
<a href="/default" up-href="/previous-page" up-scroll="restore" up-follow>
Go back
</a>
