docs: Added installation instructions (#42)

Signed-off-by: Kostis Kapelonis <[email protected]>

docs/installation.md

@@ -0,0 +1,63 @@
+# Kubernetes installation
+
+The plugin needs the main Argo Rollouts controller to work. You need to have both installed in order to perform progressive delivery
+scenarios using your Kubernetes API Gateway implementation.
+
+## Installing the Argo Rollouts controller
+
+First get the core Argo Rollouts controller in your cluster.
+
+Follow the [official instructions](https://argo-rollouts.readthedocs.io/en/stable/installation/) to install Argo Rollouts.
+
+Optionally instal the [Argo Rollouts CLI](https://argoproj.github.io/argo-rollouts/features/kubectl-plugin/) in order to control Rollouts from your terminal.
+
+## Installing the plugin
+
+To install the plugin create a configmap with the following syntax:
+
+```yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: argo-rollouts-config # must be so name
+  namespace: argo-rollouts # must be in this namespace
+data:
+  trafficRouterPlugins: |-
+    - name: "argoproj-labs/gatewayAPI"
+      location: "https://github.com/argoproj-labs/rollouts-plugin-trafficrouter-gatewayapi/releases/download/<version>/gateway-api-plugin-<arch>"
+```
+
+You can find the available versions and architectures at the [Releases page](https://github.com/argoproj-labs/rollouts-plugin-trafficrouter-gatewayapi/releases).
+
+For example for a Linux/x86 cluster save the following in a file of your choosing e.g. `gateway-plugin.yml`.
+
+```yaml
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: argo-rollouts-config # must be so name
+  namespace: argo-rollouts # must be in this namespace
+data:
+  trafficRouterPlugins: |-
+    - name: "argoproj-labs/gatewayAPI"
+      location: "https://github.com/argoproj-labs/rollouts-plugin-trafficrouter-gatewayapi/releases/download/v0.2.0/gateway-api-plugin-linux-amd64"
+```
+
+Deploy this file with `kubectl -f gateway-plugin.yml -n argo-rollouts`. You can also use [Argo CD](https://argoproj.github.io/cd/) or any other Kubernetes deployment method that you prefer.
+
+## Verifying the installation
+
+Restart the Argo Rollouts controller so that it detects the presence of the plugin.
+
+```
+kubectl rollout restart deployment -n argo-rollouts argo-rollouts
+```
+
+Then check the controller logs. You should see a line for loading the plugin:
+
+```
+time="XXX" level=info msg="Downloading plugin argoproj-labs/gatewayAPI from: https://github.com/argoproj-labs/rollouts-plugin-trafficrouter-gatewayapi/releases/download/v0.2.0/gateway-api-plugin-linux-amd64"
+time="YYY" level=info msg="Download complete, it took 7.792426599s" 
+```
+
+You are now ready to use the Gateway API in your [Rollout definitions](https://argoproj.github.io/argo-rollouts/features/specification/). 

mkdocs.yml

@@ -16,6 +16,7 @@ markdown_extensions:
     permalink: true
 nav:
 - Overview: index.md
+- Installation: installation.md
 - Providers: provider-status.md
 - Features: 
   - Advanced Deployments: features/advanced-deployments.md