feat(refacto): move everything in internal package

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

internal/generator/helper.go

@@ -0,0 +1,20 @@
+package generator
+
+import (
+	_ "embed"
+	"github.com/katenary/katenary/internal/generator/labels"
+	"strings"
+)
+
+// helmHelper is a template for the _helpers.tpl file in the chart templates directory.
+//
+//go:embed helmHelper.tpl
+var helmHelper string
+
+// Helper returns the _helpers.tpl file for a chart.
+func Helper(name string) string {
+	helmHelper := strings.ReplaceAll(helmHelper, "__APP__", name)
+	helmHelper = strings.ReplaceAll(helmHelper, "__PREFIX__", labels.KatenaryLabelPrefix)
+	helmHelper = strings.ReplaceAll(helmHelper, "__VERSION__", "0.1.0")
+	return helmHelper
+}