reacquaint ourselves with the docs

Nobody has claimed this yet.

We have docs published here https://docs.flintlock.dev/ .

They were generated from our **dev** markdown docs (found in `docs/` I believe) late in 2021 . (Personally I am not sure how, hopefully there will be something in the original PR.)

What we need are **user facing** docs (as well as dev ones) and a nicely documented process of how to alter/generate/publish them.

The docs are also fairly underdeveloped visually: we still have the placeholder images/icons which [docusaurus](https://docusaurus.io/) comes with. We should update to use our own svgs which we now have.

So, outcomes:
- The existing docs are reviewed, restructured and rebranded.
- The main "theme" of the docs should be "How do I, as a user, create Microvms with flintlock". Including (but not limited to):
- An easy getting started guide
- More advanced options
- How to provision flintlock
- Microvm spec examples (in json and Go client snippets)
- How to interact with flintlock using the recognised tools ([fl](https://github.com/weaveworks-liquidmetal/fl), [hammertime](https://github.com/warehouse-13/hammertime), etc)
- Any troubleshooting notes
- There should be another clearly marked section for **developing** flintlock (basically what we have now, just moved under a clear tab/page/whatever)
- A repo doc explaining how the docs are built and how to develop/update them

***Note: as for publishing the site with the updates, this may need to be handled by a teammember as I am not sure we have automation around that right now***

Start by reviewing the existing docs/ markdown and the published site at docs.flintlock.dev, then identify how the Docusaurus site is currently generated and published. Done means the docs are restructured around user workflows, retain a clearly separated development section, use the available SVGs, and include a repository guide for building and updating them.

Written by the indexing model from the issue text.