add badges to readme and fix minor issue in ci

.github/workflows/build-push.yml

@@ -5,7 +5,7 @@ on:
     paths:
       - ./Dockerfile
     branches:
-      - master ]
+      - master
   create:
     tags:
       - v*

README.md

@@ -1,7 +1,14 @@
+[![Docker Pulls](https://img.shields.io/docker/pulls/wasfree/toolkit)](https://hub.docker.com/repository/docker/wasfree/toolkit)
+[![Docker Build](https://img.shields.io/github/workflow/status/wasfree/toolkit/build-push)](https://github.com/wasfree/toolkit/actions?query=workflow%3Abuild-push)
+
 # Toolkit container
 
 This container will provide all required tools to debug Kubernetes cluster issues.
 
+## Prerequisites
+- [kubectl](https://kubernetes.io/de/docs/tasks/tools/install-kubectl/)
+- [kubeconfig](https://kubernetes.io/docs/tasks/access-application-cluster/configure-access-multiple-clusters/) (working kubeconfig for your cluster)
+
 ## Quick Start
 
 Deploy toolkit container as pod into your Kubernetes cluster and login: