[Contributing][Documentation] add order of translation formats

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | 
I chose XML here because the code block basically is an XML code block. I don't know if it wasn't confusing for people when we'd use Xliff here since you can't ``xliff`` as a ``code-block`` argument, can you?

Changing the order is indeed a good idea though for the reasons that you listed. We would then just have to change the order of already existing examples too. But that shouldn't be big problem.