feat(refacto): move everything in internal package

This allows to install katenary with `go install` and to clean up the
project folder.

internal/generator/extrafiles/readme.tpl

@@ -0,0 +1,32 @@
+# {{ .Chart.Name }}
+
+{{ .Chart.Description }}
+
+## Installing the Chart
+
+To install the chart with the release name `my-release`:
+
+```bash
+# Standard Helm install
+$ helm install  my-release {{ .Chart.Name }}
+
+# To use a custom namespace and force the creation of the namespace
+$ helm install my-release --namespace my-namespace --create-namespace {{ .Chart.Name }}
+
+# To use a custom values file
+$ helm install my-release -f my-values.yaml {{ .Chart.Name }}
+```
+
+See the [Helm documentation](https://helm.sh/docs/intro/using_helm/) for more information on installing and managing the chart.
+
+## Configuration
+
+The following table lists the configurable parameters of the {{ .Chart.Name }} chart and their default values.
+
+| {{ printf "%-*s" .DescrptionPadding "Parameter" }} | {{ printf "%-*s" .DefaultPadding "Default" }} |
+| {{ repeat "-" .DescrptionPadding  }} | {{ repeat "-" .DefaultPadding }} |
+{{- range .Chart.Values }}
+{{ . }}
+{{- end }}
+
+