Update documentation

Author: anahan

README.md

@@ -1,2 +1,12 @@
 # mongodb-jaeger-collector
 MongoDB's driver CommandSubscriber interface implementation for Jaeger
+
+How to use
+```php
+\MongoDB\Driver\Monitoring\addSubscriber(
+    new \CodeTool\Jaeger\MongoDb\JaegerMongoDbQueryTimeCollector(
+        $tracer,
+        new \CodeTool\Jaeger\MongoDb\CommandToStringConvertor()
+    )
+);
+```