feat(refacto): move everything in internal package

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

internal/generator/labels/labelstructs/valueFrom.go

@@ -0,0 +1,13 @@
+package labelstructs
+
+import "gopkg.in/yaml.v3"
+
+type ValueFrom map[string]string
+
+func GetValueFrom(data string) (*ValueFrom, error) {
+	vf := ValueFrom{}
+	if err := yaml.Unmarshal([]byte(data), &vf); err != nil {
+		return nil, err
+	}
+	return &vf, nil
+}