Add call to action to theme demos

[pxpm]

Viewing our demo it's easy to overlook the theme config options.

I think we should add a card or something to highlight that user can click there to explore more options. something like:

Switch themes and layouts with a click of a button. Click here to know more about it.

[welcome]

Hello there! Thanks for opening your first issue on this repo!

Just a heads-up: Here at Backpack we use Github Issues only for tracking bugs. Talk about new features is also acceptable. This helps a lot in keeping our focus on improving Backpack. If you issue is not a bug/feature, please help us out by closing the issue yourself and posting in the appropriate medium (see below). If you're not sure where it fits, it's ok, a community member will probably reply to help you with that.

Backpack communication mediums:

• Bug Reports, Feature Requests - Github Issues (here);
• Quick help (How do I do X) - Gitter Chatroom;
• Long questions (I have done X and Y and it won't do Z wtf) - Stackoverflow, using the backpack-for-laravel tag;

Please keep in mind Backpack offers no official / paid support. Whatever help you receive here, on Gitter, Slack or Stackoverflow is thanks to our awesome awesome community members, who give up some of their time to help their peers. If you want to join our community, just start pitching in. We take pride in being a welcoming bunch.

Thank you!

--
Justin Case
The Backpack Robot