Add common includes, views, and templates to proto kit docs

[jrbarnes9]

GDS's prototype kit comes with a 'docs' folder which includes a bunch of common includes, views and templates the user can simply copy and paste into their own prototype. This includes commons patterns most users will need, such as, a start page, a question, summary, confirmation.

This YouTube video demonstrates just how simply it is to use: https://www.youtube.com/watch?v=_7sNrp5KIKg

Ours would much be easier for designers with a low technical knowledge to use if we took a similar approach.