Main index html banner is not mobile responsive

[clemensutschig]

Is taken on a mobile Chrome on android
@rattermeyer / @tjaeschke - fyi ...

the code is pretty interesting to me ...

      <div class="btn-group btn-group-lg pb-0" role="group">
             *<a href*="{{site.baseurl}}/doc/getting-started" class="btn btn-primary">Installation Guide</a>
             *<a href*="https://github.com/opendevstack" class="btn btn-primary">Visit our repository</a>
      </div>

could we just introduce flex-wrap: wrap; - based on https://stackoverflow.com/questions/41625258/button-group-not-wrapping-when-too-long

[clemensutschig]