test against opencast 18 as well

Author: bluetom

.github/workflows/config.json

@@ -1,11 +1,11 @@
 {
   "main-moodle": "MOODLE_500_STABLE",
-  "main-php": "8.3",
-  "main-oc": "17.1",
-  "ocs": ["17.1", "16.7", "15.11"],
+  "main-php": "8.4",
+  "main-oc": "17.8",
+  "ocs": ["18.1", "17.8", "16.7", "15.11"],
   "main-db": "mariadb",
   "moodle-php": {
-    "MOODLE_500_STABLE": ["8.2", "8.3"]
+    "MOODLE_500_STABLE": ["8.2", "8.3", "8.4"]
   },
-  "moodle-plugin-ci": "4.5.6"
+  "moodle-plugin-ci": "4.5.8"
 }