Add screen: About

[heloa-net]

Decide about content and links that will go in this screen

[heloa-net]

@lucasbento Can you help me with suggestions on what we should have on this screen?

[lucasbento]

• Add name of each organizer (Dan Vitoriano, Lucas Bento, Nic Marcondes, Ronaldo Lima, Sebastian Ferrari, Sibelius Seraphini);
• Add an onPress on each one of them to open an action sheet that should provide links to the twitter and github;
• Add link to github org (@react-brasil);
• Add link to conf site (reactconfbr.com.br);
• Add section about the creator of the app (The greatest Heloá of all time) and link to source-code (add a dumb one, we will fix later on).