Add tutorial for creating a basic prototype (based on GOV.UK one)

[vickytnz]

Description

This is probably not quite ready to go straight to deployment because it has:

1. example pages to help with debugging or screenshots - these probably need to be deleted
2. a nunjucks base page with variables to help with change pages before it is resolved
3. code formatting that could be tidier
4. a few little elements of the nhs components that aren't yet in the code (for example, deleting the paragraph at the bottom of each template page that links to the templates)

It does have a full worked example bringing together the content into a guide.

Example of translated screenshots that are used in the examples

It's also shown that some of the design system components can do with tweaking, for example:

1. radio examples don't have the same text in the text as the variable
2. radio example in component library starts with yes/no, unlike govuk design system which starts with list of 3
3. textarea component doesn't have headers shown

Checklist

• [ ] Tested against our testing policy (Resolution, Browser & Accessibility)
• [ ] CHANGELOG entry

Resolves #17

[vickytnz]

Current status is that this is in a good place for review:

• there may be a few little code things with styling that aren't 100% with the GOV.UK version (whether things are styled as code or strong etc)
• I've removed the example pages but deliberately left all the new content as variables in the base page just to make sure any changes happen across all pages - it could be that they can be hard-coded but it was so tricky to find everything that I don't want to remove them just yet

[vickytnz]

Need to link from the install guide - will make separate pull request.