Add documentation

README.md

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 # gdscan
-Helm Chart for GD Scan 
+
+This Helm chart deploys GD Scan, an HTTP-based virus scanner. 
+
+<img src="GD Scan Server.png" alt="GDScan" style="width:50%">
+
+The chart deploys one pod, consisting of two containers:
+ * GD Scan Server that is responsible for scanning. It contains two scan engines, which are Bitdefender and G DATA.
+ * GD Scan Client that initiates scans and receive results. The client is wrapped by an HTTP API.
+
+
+## Usage
+
+Since Docker images for the scan server and client are located in a private GitHub repository, you need username and password for pulling. The authentication requires some prerequisites:
+
+1. Create a string in the format $USERNAME:$PASSWORD and encode it to base64. 
+
+2. Create a docker.config JSON file:
+```
+{
+    "auths": {
+        "ghcr.io": {
+            "auth": "$$_BASE64_ENCODED_USER_NAME_AND_PASSWORD_$$"
+        }
+    }
+}
+```
+3. Encode docker.config to base64 and copy it into a values.yaml file:
+
+```
+secret: 
+    dockerconfigjson: $$_BASE64_ENCODED_DOCKER_CONFIG_$$
+```
+
+4. Add GD Scan repository:
+
+```
+helm repo add gdscan https://gdatasoftwareag.github.io/gdscan/
+```
+
+5. Now you are able to start GD Scan:
+
+```
+helm install gdscan gdscan/gdscan -f values.yaml
+```
+
+For further information about usage, please checkout the application's Swagger UI.
+
+## Credentials
+
+If you are interested and want to use the GD Scan by yourself, please [contact us](mailto:[email protected]).