Make heading sizes consistent.

README.md

@@ -77,7 +77,7 @@ See the [Javadoc in the XmlWriter](https://javadoc.io/doc/org.cthing/xmlwriter/l
 usage and configuration information. See the [State Machine document](dev/docs/StateMachine.md) for details on the formatter state machine
 at the heart of the `XmlWriter` class.
 
-### Building
+## Building
 The library is compiled for Java 17. If a Java 17 toolchain is not available, one will be downloaded.
 
 Gradle is used to build the library:
@@ -89,7 +89,7 @@ The Javadoc for the library can be generated by running:
 ./gradlew javadoc
 ```
 
-### Releasing
+## Releasing
 This project is released on the [Maven Central repository](https://central.sonatype.com/artifact/org.cthing/xmlwriter).
 Perform the following steps to create a release.