Add usage and warning in README

[skip build]

Author: Nicolas Perraut

README.md

@@ -1,6 +1,9 @@
 # Tunack
 
+:warning: Tunack is under heavy development, __NOT SUITABLE FOR PRODUCTION__ (or at your own risks). PR are warmly welcomed
+
 Tcp and Udp Nginx Auto Config in Kubernetes
+
 Auto configuration service for TCP and UDP services for Kubernetes Nginx ingress manager
 
 ## Getting Started
@@ -20,6 +23,38 @@ kubectl apply -f https://raw.githubusercontent.com/mafzst/tunack/v0.1.0/deploy/w
 
 It will create a deployement in `ingress-nginx` namespace
 
+## Usage
+
+Tunack uses annotations in services to detect ports to expose.
+
+### Synopsis
+
+`tunack.dahus.io/[protocol]-service-[proxyPort]: [servicePort]`
+
+- __protocol__: `tcp|udp`: Specify service type
+- __proxyPort__: Port to export to outside (ie. public port)
+- __servicePort__: Target service port (ie. port on which your service is listening to)
+
+__ONLY TCP IS IMPLEMENTED YET__
+
+### Example
+
+``` yaml
+apiVersion: v1
+kind: Service
+metadata:
+  name: my-tcp-service
+  annotations:
+    - tunack.dahus.io/tcp-service-3000: 80
+spec:
+  ports:
+  - port: 80
+    targetPort: 8080
+  selector:
+    app: my-tcp-service
+
+```
+
 ## Contributing
 
 Please read [CONTRIBUTING.md](CONTRIBUTING.md) for details on our code of conduct, and the process for submitting pull requests to us.