[Translation] Allow choosing instance/backend for translating

[Rumperuu]

The translation skill currently uses https://lingva.ml, an instance of the alternative Lingva Translate frontend for Google Translate (see #10). However, https://lingva.ml is no longer functional, so the Dicio translation skill does not work any more.

As far as I can tell, the Lingva repo (https://github.com/TheDavidDelta/lingva-translate) was last updated 4 years ago. I assume the project is dead.

Based on the list of instances in that repo's README, only the following are still live:

• https://translate.plausibility.cloud/
• https://lingva.lunar.icu/
• https://translate.projectsegfau.lt/ (now using Mozhi)
• https://lingva.garudalinux.org/

There is also SimplyTranslate, which I personally use.

[Stypox]

It seems to work again now so I updated the title. But yeah I definitely agree the instance should be choosable.