README.md: fix missing newline

Follow up #541

Signed-off-by: Kentaro Hayashi <hayashi@clear-code.com>

Author: kenhys

README.md

@@ -178,6 +178,7 @@ With the introduction of the rdkafka-ruby based input plugin we hope to support
 See also [rdkafka-ruby](https://github.com/appsignal/rdkafka-ruby) and [librdkafka](https://github.com/edenhill/librdkafka/blob/master/CONFIGURATION.md) for more detailed documentation about Kafka consumer options.
 
 `topics` supports POSIX Extended Regular Expression pattern (not Ruby regex syntax) since v0.19.6. If you want to use regex pattern, use `/pattern/` like `/foo.*/`.
+
 **Note**: A caret (`^`) is automatically added to the beginning of the pattern.
 
 Consuming topic name is used for event tag. So when the target topic name is `app_event`, the tag is `app_event`. If you want to modify tag, use `add_prefix` or `add_suffix` parameter. With `add_prefix kafka`, the tag is `kafka.app_event`.