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
* Adjust names of tasks.
* Add composer require checker.
* Install without plugins to not use custom installer and stay
compatible with require checker.
* Stay phpunit 10 compatible.
