[TASK] Add info to UPGRADE.md

UPGRADE.md

+## Version 4.4  ```project_theme_lightbox``` integration
+- The magnific popup integration is deprecated and will be removed in later versions.
+- Implement JavaScript according to the readme after integrating ```project_theme_lightbox```
+
 ## Version 4 Breaking Changes
 
 - Dropped TYPO3 8 support