Restructure Introduction pages

[richierocks]

Welcome

1. Add a little "why are we here?" preamble.
2. Split 'Types of content into its own page, and move into 'Getting started' Section

Getting Started

Split this into several pages.

1. Choosing your content type
2. Then setting up Asana
3. Registering with DataCamp
4. Setting up GitHub

Edit those pages to link to the Technical Help Resources page (content currently duplicated).

Move Auditioning and Contract stuff here?