Update maven dependency sections in the README

Author: fjuma

README.md

@@ -29,11 +29,14 @@ The A2A Java SDK provides a Java server implementation of the [Agent2Agent (A2A)
 
 ### 1. Add the A2A Java SDK Core Maven dependency to your project
 
+> **Note**: The A2A Java SDK isn't available yet in Maven Central but will be soon. For now, be
+> sure to check out the latest tag (you can see the tags [here](https://github.com/fjuma/a2a-java-sdk/tags)), build from the tag, and reference that version below. For example, if the latest tag is `0.2.3`, you can use the following dependency.
+
 ```xml
 <dependency>
     <groupId>io.a2a.sdk</groupId>
     <artifactId>a2a-java-sdk-core</artifactId>
-    <version>${io.a2a.sdk.version}</version>
+    <version>0.2.3</version>
 </dependency>
 ```
 
@@ -222,6 +225,9 @@ public class WeatherAgentExecutorProducer {
 
 ### 4. Add an A2A Java SDK Server Maven dependency to your project
 
+> **Note**: The A2A Java SDK isn't available yet in Maven Central but will be soon. For now, be
+> sure to check out the latest tag (you can see the tags [here](https://github.com/fjuma/a2a-java-sdk/tags)), build from the tag, and reference that version below. For example, if the latest tag is `0.2.3`, you can use the following dependency.
+
 Adding a dependency on an A2A Java SDK Server will allow you to run your agentic Java application as an A2A server.
 
 The A2A Java SDK provides two A2A server endpoint implementations, one based on Jakarta REST (`a2a-java-sdk-server-jakarta`) and one based on Quarkus Reactive Routes (`a2a-java-sdk-server-quarkus`). You can choose the one that best fits your application.