Document some temporary workarounds (#986)

README.md

@@ -89,6 +89,56 @@ be detected when using `-Dbenchmark`, however, `FooBar` will be ignored.
 
 See also: [documentation for JMH benchmarks](https://github.com/jenkinsci/jenkins-test-harness/blob/master/docs/jmh-benchmarks.adoc)
 
+## Temporary workarounds
+
+### Running tests with Jetty 12 (EE 8)
+
+To run tests with Jetty 12 (EE 8) with Jenkins 2.471 or older,
+add the following to `pom.xml`:
+
+```xml
+<!-- TODO JENKINS-73339 until in parent POM -->
+<jenkins-test-harness.version>2254.vcff7a_d4969e5</jenkins-test-harness.version>
+<maven.compiler.testRelease>17</maven.compiler.testRelease>
+```
+
+This will not be necessary in a future release of the plugin parent POM that requires Jenkins 2.472 or newer.
+
+### Running the entire build with Jetty 12 (EE 8):
+
+To run the entire build with Jetty 12 (EE 8) and require Jenkins 2.472 or newer,
+add the following to `pom.xml` (adjusting your BOM version as necessary):
+
+```xml
+<jenkins.version>2.472</jenkins.version>
+<!-- TODO JENKINS-73339 until in parent POM -->
+<jenkins-test-harness.version>2254.vcff7a_d4969e5</jenkins-test-harness.version>
+<maven.compiler.release>17</maven.compiler.release>
+```
+
+This will not be necessary in a future release of the plugin parent POM that requires Jenkins 2.472 or newer.
+
+### Running the entire build with Jetty 12 (EE 9):
+
+To run the entire build with Jetty 12 (EE 9),
+first follow the steps in the preceding section,
+then add the following to `pom.xml`:
+
+```xml
+<dependencyManagement>
+  <dependencies>
+    <!-- TODO JENKINS-73339 until in parent POM, work around https://github.com/jenkinsci/plugin-pom/issues/936 -->
+    <dependency>
+      <groupId>jakarta.servlet</groupId>
+      <artifactId>jakarta.servlet-api</artifactId>
+      <version>5.0.0</version>
+    </dependency>
+  </dependencies>
+</dependencyManagement>
+```
+
+This will not be necessary in a future release of the plugin parent POM that requires Jetty 12 EE 9 or newer.
+
 ## Javadoc
 
 Javadoc has been set to _quiet_ by default in 2.20+, which means it will only log errors and warnings.