Add minio guide

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

Author: SISheogorath

docs/guides/images/minio-image-upload/create-bucket.png

@@ -0,0 +1,83 @@
+Minio Guide for HackMD
+===
+
+1. First of all you need to setup Minio itself.
+
+   Please refer to the [official Minio docs](https://docs.minio.io/) for an
+   production setup.
+
+   For checking it out and development purposes a non-persistent setup is enough:
+   ```console
+   docker run --name test-minio --rm -d -p 9000:9000 minio/minio server /data
+   ```
+
+   *Please notice this is not for productive use as all your data gets lost
+   when you stop this container*
+
+2. Next step is to get the credentials form the container:
+
+   ```
+   docker logs test-minio
+   ```
+
+   ![docker logs](images/minio-image-upload/docker-logs.png)
+
+3. Open http://localhost:9000 and login with the shown credentials.
+
+   ![minio default view](images/minio-image-upload/default-view.png)
+
+4. Create a bucket for HackMD
+
+   ![minio create bucket](images/minio-image-upload/create-bucket.png)
+
+5. Add a policy for the prefix `uploads` and make it read-only.
+
+   ![minio edit policy](images/minio-image-upload/open-edit-policy.png)
+   *Open policy editor*
+
+   ![minio policy adding](images/minio-image-upload/create-policy.png)
+   *Add policy for uploads*
+
+6. Set credentials and configs for Minio in HackMD's `config.json`
+
+   ```JSON
+   "minio": {
+     "accessKey": "888MXJ7EP4XXXXXXXXX",
+     "secretKey": "yQS2EbM1Y6IJrp/1BUKWq2/XXXXXXXXXXXXXXX",
+     "endPoint": "localhost",
+     "port": 9000,
+     "secure": false
+   }
+   ```
+   *You have to use different values for `endpoint` and `port` for a production
+   setup. Keep in mind the `endpoint`-address has to be public accessible from
+   your browser.*
+
+7. Set bucket name
+
+   ```JSON
+   "s3bucket": "hackmd"
+   ```
+
+8. Set upload type.
+
+   ```JSON
+   "imageUploadType": "minio"
+   ```
+
+9. Review your config.
+
+   ```json
+   {
+     // all your other config…
+     "minio": {
+       "accessKey": "888MXJ7EP4XXXXXXXXX",
+       "secretKey": "yQS2EbM1Y6IJrp/1BUKWq2/XXXXXXXXXXXXXXX",
+       "endPoint": "localhost",
+       "port": 9000,
+       "secure": false
+     },
+     "s3bucket": "hackmd",
+     "imageUploadType": "minio"
+   }
+   ```