TYPO3 12 support

[fnagel]

Update extension for TYPO3 CMS 12 LTS.

Release is planned for end of this summer. Hopefully. Any help is appreciated!

WIP branch: https://github.com/fnagel/generic-gallery/tree/typo3-12

References

• https://get.typo3.org/release-notes/12.0.0
• https://docs.typo3.org/c/typo3/cms-core/main/en-us/Changelog-12.html
• https://notes.typo3.org/s/EjM2zA7Dr

[fnagel]

WIP branch should be working now. Feedback is appreciated!

[fnagel]

Version 6.0.0 with support for TYPO3 12 has been released: https://github.com/fnagel/generic-gallery/releases/tag/6.0.0