[Feature]: Add support for Arabic as a source/target language

[kill9zombie]

Description

Deepl now supports Arabic for text translation:

https://developers.deepl.com/docs/resources/supported-languages#target-languages

While Arabic isn't supported for document translation, it is supported for text translation now.

Type of change

• New feature (non-breaking change which adds functionality)

How Has This Been Tested?

• With the following .exs script (and an appropriate Deepl API key in ~/.deepl.apikey):

# scripts/arabic-test.exs
key = File.read!("#{System.get_env("HOME")}/.deepl.apikey")
Application.put_env(:deepl_ex, :api_key, String.trim(key))

DeeplEx.translate("hello", :EN, :AR) |> IO.inspect()
DeeplEx.translate("مرحباً", :AR, :EN) |> IO.inspect()

• Run using mix run

mix run scripts/arabic-test.exs

{:ok, "مرحباً"}
{:ok, "Hey there."}

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• My changes generate no new warnings

[dustessavdh]

LGTM!

[dustessavdh]

Thank you for your PR, I'll merge it soon and make a new release!