Initial documentation website

[nojaf]

@dawedawe and I wish to add more documentation to encourage people to write their own analyzers.
So far I have:

• done an initial fsharp.formatting setup
• enjoyed myself with some CSS
• Added a first very basic page with Getting started

Other ideas (for later PRs) we have are:

• A recipe page, where we elaborate on how certain information can be acquired from the Context.
• Adding a guide on writing unit tests
• An overview of existing analyzers in the wild.
• Implement search via Algolia.
• Try and set up a way to view docs per released version.

All of this is WIP but I think this is a good enough first chunk for now.