docs: add docusaurus docs

* Created website for the docs inside /docs

* remove old docs and home page

* fix wrong redirection path

* remove most of the docs from the readme

* fix docs path

* undo package.json changes

* remove unused images

* rename "how to" route

---------

Co-authored-by: Elias Schneider <login@eliasschneider.com>

docs/docs/setup/upgrading.md

@@ -0,0 +1,44 @@
+---
+id: upgrading
+---
+
+# Upgrading
+
+### Upgrade to a new version
+
+As Pingvin Share is in early stage, see the release notes for breaking changes before upgrading.
+
+#### Docker
+
+```bash
+docker compose pull
+docker compose up -d
+```
+
+#### Stand-alone
+
+1. Stop the running app
+   ```bash
+   pm2 stop pingvin-share-backend pingvin-share-frontend
+   ```
+2. Repeat the steps from the [installation guide](#stand-alone-installation) except the `git clone` step.
+
+   ```bash
+   cd pingvin-share
+
+   # Checkout the latest version
+   git fetch --tags && git checkout $(git describe --tags `git rev-list --tags --max-count=1`)
+
+   # Start the backend
+   cd backend
+   npm install
+   npm run build
+   pm2 restart pingvin-share-backend
+
+   # Start the frontend
+   cd ../frontend
+   npm install
+   npm run build
+   API_URL=http://localhost:8080 # Set the URL of the backend, default: http://localhost:8080
+   pm2 restart pingvin-share-frontend
+   ```