WIP: (Spike) Build and publish styleguidist documentation

This MR delivers a CI/CD pipline that builds the styleguidist documentation for common components. Updating any component triggers this project to generate the documentation for all the components and publish it to GitHub Pages.

This is a spike, so I'd like to see if we think this is in broadly the right shape. There are a couple of wrinkles that I can see.

• Given all the documentation is built at once, having a seperate project for this seems correct. However, if code is merged that styleguidist can't compile, the build process will only fail the documentation. From this point of view, it may be better build the documentation in the component projects.
• We're currently getting a 404 on the GitHub page and I can't see what is wrong (might be related to it being organisation account - works for a user account). A way around this could be to create a new free github user account (ucam_uis_devops_react or similar) and publish to that.

Possibly closes: #1 (closed)