This commit introduces support for the Mullvad Leta search backend, which is now enabled by default. It includes a new conversion function to transform Leta's search results into a format compatible with Whoogle. The README has been updated to reflect this change, detailing the limitations of the Leta backend and how to switch back to Google if needed. Additionally, the configuration model has been updated to include a setting for enabling/disabling the Leta backend.
* Sync setup.cfg with requirements.txt
* Include tests in PyPI tarballs
And exclude them from setuptools
* Set version number only once
Switch to PEP517 standard (pyproject.toml) for builds