Add support for DeepL and/or Microsoft Azur

[WiliTest]

It would be even better if it could work with DeepL and/or Microsoft Azure.

This would make this app much more popular.

(It has already been requested here)

I did a little research and found that the free version we are using isn't documented at all. I think it is an old endpoint keep for backward compatibility reasons. I also found that Google Cloud APIs for batch traduction requires an account with billing setup.

Furthermore, I use another translator since a while called DeepL, they have a fresh API with free plan of 500k chars a month. The API supports batch translation, by sending multiple sentences at once and adding context to the translation. The only drawback it that it needs an API key along with an account.

DeepL does the same thing as Google, and could be even better in certain cases.
Has a better API and is well documented.
Doesn't require a complex account setup. A quick tutorial in the readme should do the trick.
Maybe, we could implement the functionality with DeepL API but keep Google API wonky translations as an alternative. Tell me what you think.

Links
DeepL API docs.
Google Cloud Translation API