Implement Repository Homepage for Mobile

Repomaker should create a repository homepage that allows the user to add the repository easily.

Due to the different workflows, there should be different views depending on whether the user is already using a mobile phone or a desktop computer. We still need to determine where to implement this: directly in repomaker, in fdroidserver or some new small library.

This ticket is for implementing the repository homepage for mobiles.

Design

Here are some quick specs: FONTS h1 Roboto bold 18px p Roboto regular 12px button Roboto medium 11px

COLORS blue highlight: 0066CC gray outline button and text: 58595B

I'll also add a placeholder image for the apps.