TYPO3 v10 compatibility

I am working on a PR to make this extension v10 compatible. The extension accesses $GLOBALS['TYPO3_CONF_VARS']['EXT']['extConf'] to read configurations, which is deprecated in TYPO3 9 and removed in 10. We can use Extension configuration API It also uses FileProcessingService signal. Using signals are deprecated in TYPO3 V10 and will be removed in v10. We can use BeforeFileProcessingEvent class's onFileProcessingServiceEmitPreFileProcessSignal event instead of preProcess signal.

To remove the deprecated code support of TYPO3 8 and 9 should be dropped. Is it OK to remove support of older versions of TYPO3?