Add localization translation feature using DeepL API

Add localization translation feature using DeepL API: a task in LegoFlow-SWE (Harbor dataset). Theia currently has no automated way to translate its own localization JSON files into multiple languages. Manually translating every string for 10+ languages on every PR is not feasible. We need a CLI…

The task

Theia currently has no automated way to translate its own localization JSON files into multiple languages. Manually translating every string for 10+ languages on every PR is not feasible. We need a CLI command and programmatic API that uses the DeepL machine translation service to translate missing entries.

Part of Lego-X/LegoFlow-SWE.