add rdkafka5 (#51)

Author: nick-zh

composer.json

@@ -18,7 +18,7 @@
   ],
   "require": {
     "php": "^7.3",
-    "ext-rdkafka": "^4.0.0",
+    "ext-rdkafka": "^4.0|^5.0",
     "ext-json": "*"
   },
   "require-dev": {