Add Back Button To Vue

[sGerli]

1. Add back button on all pages except App's home and Watchface's home.

The back button code is: (Goes inside navbar like in here)

<div class="navbar__items left">
   <a class="float-xs-left back" href="app-details.html"><i class="fa fa-angle-left" aria-hidden="true"></i></a>
</div>

[Zetaphor]

Fixed in #77