[TASK] Prepare extension version constraints for TYPO3 v9 support

composer.json

@@ -9,7 +9,7 @@
         "issues": "https://git-t3o.typo3.org/t3o/t3o_membership/issues"
     },
     "require": {
-        "typo3/cms-core": "8.5.0 - 8.9.99",
+        "typo3/cms-core": "8.5.0 - 9.9.99",
         "lukebaird/dropbox-v2-php-sdk": "^1.1"
     },
     "autoload": {