- Adds support for translating Python strings and .UI files with Qt's `QTranslator` class.
- Integrates the Transifex cloud translation service for managing translations.
- Adds translation policy and guidelines to `CONTRIBUTING.md`
* Simplify non-blocking BorgThread.run.
* Fix issue with displaying nested folders in extract-dialog.
* Fix error text expansion.
* Add many new tests. Dont open main window on startup.