Add support for SimplyTranslate

[bigdiff]

https://git.sr.ht/~metalune/simplytranslate_web/tree/HEAD/api.md

simply translate is a proxy service for google translate and other translation services.

it helps protect user privacy by not directly connecting to google for translations and not exposing user ip address.

their api is pretty straight forward.

[rafaelmardojai]

You already can use Lingva Translate that does the same.

[begin-theadventure]

You already can use Lingva Translate that does the same.

Nevertheless, SimplyTranslate is a different project and there are different instances for it, so I think it would be great to have it as an option.
In addition, since the last commit on January 13 (2023), the project is no longer maintained and the official instance has stopped working.