Update the README with details of dev builds.

README.md

@@ -12,14 +12,47 @@ This library uses [Spring Security](https://spring.io/projects/spring-security)
 
 This [library](https://search.maven.org/artifact/uk.ac.ox.ctl/spring-security-lti13) is released to maven central and can be added to your maven project with the following project coordinates:
 
+```xml
     <dependency>
         <groupId>uk.ac.ox.ctl</groupId>
         <artifactId>spring-security-lti13</artifactId>
         <version>0.2.0</version>
     </dependency>
+```
 
 There is a [demo project](https://github.com/oxctl/spring-security-lti13-demo) built using this library that may be helpful in getting started with the project.
 
+### Development Builds
+
+If you want to use the latest (unstable) unreleased version of the library in your project builds are published to GitHub packages. To use this version in your project you need to add the GitHub packages repository to your `pom.xml`:
+
+```xml
+    <repositories>
+        <repository>
+            <id>oxctl/spring-security-lti13</id>
+            <url>https://maven.pkg.github.com/oxctl/spring-security-lti13</url>
+            <snapshots>
+                <enabled>true</enabled>
+            </snapshots>
+            <releases>
+                <enabled>false</enabled>
+            </releases>
+        </repository>
+    </repositories>
+```
+
+then add the `SNAPSHOT` version of the library to your `pom.xml`:
+
+```xml
+    <dependency>
+        <groupId>uk.ac.ox.ctl</groupId>
+        <artifactId>spring-security-lti13</artifactId>
+        <version>0.2.1-SNAPSHOT</version>
+    </dependency>
+```
+
+However, this should just be for testing until a new version is released to Maven Central.
+
 ### Releasing
 
 The project is deployed to the central repository, once ready to release use the release plugin to tag everything: