Replace Gatsby with Docusaurus.

Gatsby is great, but brings a high level of complexity, and in this
commit, it is replaced with Docusaurus which is simpler and also
streamlined to produced versioned documentation. Things like a
collapsable sidebar, right hand side page navigation, bread-crumbs,
warning about using old site documentation, just works out of the box.

Themes (light and dark) has also been added along with a search-bar
which is backed by Google's programmable search engine.

Lots of unused images were removed.

Signed-off-by: Thomas Hallgren <[email protected]>

README.md

@@ -0,0 +1,41 @@
+# Website
+
+This website is built using [Docusaurus](https://docusaurus.io/), a modern static website generator.
+
+### Installation
+
+```
+$ yarn
+```
+
+### Local Development
+
+```
+$ yarn start
+```
+
+This command starts a local development server and opens up a browser window. Most changes are reflected live without having to restart the server.
+
+### Build
+
+```
+$ yarn build
+```
+
+This command generates static content into the `build` directory and can be served using any static contents hosting service.
+
+### Deployment
+
+Using SSH:
+
+```
+$ USE_SSH=true yarn deploy
+```
+
+Not using SSH:
+
+```
+$ GIT_USER=<Your GitHub username> yarn deploy
+```
+
+If you are using GitHub pages for hosting, this command is a convenient way to build the website and push to the `gh-pages` branch.