Setup documentation workflow

[Nyall Dawson]

[Nyall Dawson]

@jvdkwast I'll need to do a video call with you to talk you through setting this up on the github repo. Can you email me when you're online and available for this?

[Hans van der Kwast]

The GitHub page now points to readme.md instead of website/pages/index.md

[Nyall Dawson]

@jvdkwast the workflow should be working ok now -- can you set the repo settings for github pages to use the gh-pages branch again? (Like we were trying to do earlier)

[Hans van der Kwast]

@nyalldawson Done. The page shows up now.
The only thing is that the numbered lists are not taken over correctly from the index.md file.

[Nyall Dawson]

@jvdkwast that's fixed now