Update version numbers in README.md

Author: pjfanning

README.md

@@ -33,12 +33,12 @@ Specifically:
 
 ## Branches
 
-`master` branch is for developing the next major Jackson version -- 3.0 -- but there
-are active maintenance branches in which much of development happens:
+`3.x` branch is for developing the next major Jackson version -- 3.2 -- but there
+are active maintenance branches for LTS releases:
 
-* `2.19` is for developing the next minor 2.x version
-* `2.18` is for backported fixes to include in 2.18.x patch versions
-* `2.17` is for backported fixes to include in 2.17.x patch versions
+* `3.1`
+* `2.21`
+* `2.18`
 
 Older branches are usually not changed but are available for historic reasons.
 All released versions have matching git tags (`jackson-dataformat-xml-2.17.1`).
@@ -49,21 +49,39 @@ All modules are licensed under [Apache License 2.0](http://www.apache.org/licens
 
 ## Maven dependency
 
+To use Jackson 3.x compatible version of this extension on Maven-based projects, use following dependency:
+
+Maven:
+```xml
+<dependency>
+  <groupId>tools.jackson.dataformat</groupId>
+  <artifactId>jackson-dataformat-xml</artifactId>
+  <version>3.1.1</version>
+</dependency>
+```
+
+Gradle:
+```groovy
+dependencies {
+    implementation 'tools.jackson.dataformat:jackson-dataformat-xml:3.1.1'
+}
+```
+
 To use Jackson 2.x compatible version of this extension on Maven-based projects, use following dependency:
 
 Maven:
 ```xml
 <dependency>
   <groupId>com.fasterxml.jackson.dataformat</groupId>
   <artifactId>jackson-dataformat-xml</artifactId>
-  <version>2.18.1</version>
+  <version>2.21.2</version>
 </dependency>
 ```
 
 Gradle:
 ```groovy
 dependencies {
-    implementation 'com.fasterxml.jackson.dataformat:jackson-dataformat-xml:2.18.1'
+    implementation 'com.fasterxml.jackson.dataformat:jackson-dataformat-xml:2.21.2'
 }
 ```