* Support TYPO3 v12.0
All dependencies are compatible now.
We can update to support v12.0.
This commit will shift TYPO3 support from 10 and 11 to 11 and 12.
See Changelog entry.
Update dev dependencies to our latest best practice.
Auto migrate code base to follow CGL and use PHP 7.4.
Allow integrator to limit results in widget to certain languages.
If only one language is allowed, labels will be translated.
Otherwise default system language is used.
E.g. one record will be displayed in multiple languages, it would be
confusing to show him multiple times for each language.
Add TYPO3 extension for phpstan as many things would break within tests.
Relates: #15
