[doc] Add max message size configuration in doc (#9810)
Motivation
Add documentation for configuring max message size.
diff --git a/site2/docs/concepts-messaging.md b/site2/docs/concepts-messaging.md
index b9b7125..3a8f6a0 100644
--- a/site2/docs/concepts-messaging.md
+++ b/site2/docs/concepts-messaging.md
@@ -23,6 +23,21 @@
Event time | An optional timestamp attached to a message by applications. For example, applications attach a timestamp on when the message is processed. If nothing is set to event time, the value is `0`.
TypedMessageBuilder | It is used to construct a message. You can set message properties such as the message key, message value with `TypedMessageBuilder`. </br> When you set `TypedMessageBuilder`, set the key as a string. If you set the key as other types, for example, an AVRO object, the key is sent as bytes, and it is difficult to get the AVRO object back on the consumer.
+The default size of a message is 5 MB. You can configure the max size of a message with the following configurations.
+
+- In the `broker.conf` file.
+
+ ```bash
+ # The max size of a message (in bytes).
+ maxMessageSize=5242880
+ ```
+
+- In the `bookkeeper.conf` file.
+
+ ```bash
+ # The max size of the netty frame (in bytes). Any messages received larger than this value are rejected. The default value is 5 MB.
+ nettyMaxFrameSizeBytes=5253120
+ ```
> For more information on Pulsar message contents, see Pulsar [binary protocol](developing-binary-protocol.md).
## Producers
