Update the junitlauncher manual to include an example of configuring a nested classpath for including test engines

manual/Tasks/junitlauncher.html

@@ -52,7 +52,7 @@
     are necessary to run the tests are:
 </p>
 
-<ul>
+<ul id="junit-platform-libraries">
     <li>
         <samp>junit-platform-commons.jar</samp>
     </li>
@@ -62,6 +62,9 @@
     <li>
         <samp>junit-platform-launcher.jar</samp>
     </li>
+    <li>
+        <samp>opentest4j.jar</samp>
+    </li>
 </ul>
 
 <p>
@@ -69,7 +72,7 @@
     following libraries in the classpath
 </p>
 
-<p>
+<p id="junit-vintage-engine-libraries">
     For <q>junit-vintage</q> engine:
 </p>
 
@@ -82,7 +85,7 @@
     </li>
 </ul>
 
-<p>
+<p id="junit-jupiter-engine-libraries">
     For <q>junit-jupiter</q> engine:
 </p>
 
@@ -93,9 +96,6 @@
     <li>
         <samp>junit-jupiter-engine.jar</samp>
     </li>
-    <li>
-        <samp>opentest4j.jar</samp>
-    </li>
 </ul>
 
 <p>
@@ -108,6 +108,9 @@
     <li>OR Leave <samp>ant-junitlauncher.jar</samp> in the <samp>ANT_HOME/lib</samp> directory and
         include all other relevant jars in the classpath by passing them as a <kbd>-lib</kbd>
         option, while invoking Ant</li>
+    <li>OR Use the nested <code>&lt;classpath&gt;</code> element to specify the location of the
+        test engines. For more details about this approach, please read the 
+        <a href=#test-engine-in-classpath>using classpath element to include test engines</a> section.
 </ul>
 
 <p>
@@ -150,12 +153,81 @@
 </p>
 <ul>
     <li>Finding the test classes to execute</li>
+    <li>Finding test engines that run the tests</li>
 </ul>
 <p>
     If the <code>classpath</code> element isn't configured for the task, then the classpath of Ant
     itself will be used for finding the test classes.
 </p>
 
+<h5 id="test-engine-in-classpath">Using the classpath element to include test engines</h5>
+<p>
+    The <code>&lt;classpath&gt;</code> can be used to include the test engines that you want to be
+    considered for execution of the tests. 
+</p>
+<p>    
+    <strong>NOTE:</strong> An important aspect to remember is that 
+    whether or not you use this approach, the JUnit 5 platform libraries 
+    <a href="#junit-platform-libraries">listed earlier in this 
+    document</a> and the <code>ant-junitlauncher.jar</code>, <i>shouldn't</i> be part of this classpath
+    and instead they must be included in Ant runtime's classpath either by placing them 
+    in <code>ANT_HOME/lib</code> or by passing the <code>-lib</code> option.
+</p>
+<p>
+    Below is an example of setting up the classpath to include the Jupiter test engine during the
+    execution of the tests. We assume that the JUnit 5 platform libraries and the 
+    <code>ant-junitlauncher.jar</code> have been setup as explained previously.
+    <br/>
+    <pre> 
+&lt;project&gt;
+
+    &lt;property name="output.dir" value="${basedir}/build"/&gt;
+    &lt;property name="src.test.dir" value="${basedir}/src/test"/&gt;
+    &lt;property name="build.classes.dir" value="${output.dir}/classes"/&gt;
+
+    &lt;target name="init"&gt;
+        &lt;mkdir dir="${output.dir}"/&gt;
+    &lt;/target&gt;
+
+    &lt;path id="junit.engine.jupiter.classpath"&gt;
+        &lt;fileset dir="${basedir}/src/lib/jupiter/"/&gt;
+    &lt;/path&gt;
+
+    &lt;target name="compile-test" depends="init"&gt;
+        &lt;mkdir dir="${build.classes.dir}"/&gt;
+        &lt;javac srcdir="${src.test.dir}"
+           destdir="${build.classes.dir}"&gt;
+           &lt;classpath refid="junit.engine.jupiter.classpath"/&gt;
+        &lt;/javac&gt;  
+    &lt;/target&gt; 
+
+    &lt;target name="test" depends="compile-test"&gt;
+        &lt;junitlauncher&gt;
+            &lt;classpath refid="junit.engine.jupiter.classpath"/&gt;
+            &lt;classpath&gt;
+                &lt;pathelement location="${build.classes.dir}"/&gt;
+            &lt;/classpath&gt;  
+            &lt;testclasses outputdir="${output.dir}"&gt;
+                &lt;fileset dir="${build.classes.dir}"/&gt;
+                &lt;listener type="legacy-brief" sendSysOut="true"/&gt;
+                &lt;listener type="legacy-xml" sendSysErr="true" sendSysOut="true"/&gt;
+         
+            &lt;/testclasses&gt;
+        &lt;/junitlauncher&gt;
+    &lt;/target&gt; 
+&lt;/project&gt;
+    </pre>
+
+    In the example above, the <code>src/lib/jupiter</code> directory is expected to contain 
+    the Jupiter test engine related jars (which have been 
+    <a href="#junit-jupiter-engine-libraries">listed in an earlier section of this
+    document</a>). In the <code>test</code> target we use the <code>classpath</code> nested element
+    to point to the <code>junit.engine.jupiter.classpath</code> containing those jars. In this
+    <code>test</code> target we also use another <code>classpath</code> element to point to 
+    the location containing our test classes. If required, both these classpath can be combined 
+    into one.
+</p>    
+
 <h4>listener</h4>
 
 <p>