Add ollama as backend translation service

That would be great to be able to run translation service locally like https://github.com/ollama/ollama

The implementation would be really close to the openai one: https://github.com/glebm/i18n-tasks/blob/main/lib/i18n/tasks/translators/openai_translator.rb

I could open a PR if you think it's worth it

Thank you in advance