Improve random generator demo

Author: Nicolai Parlog

src/main/java/org/codefx/demo/java17/api/random/RandomGenerators.java

@@ -37,6 +37,9 @@ private static void simpleCreation() {
 		// (for implemented algorithms, see Javadoc of java.util.random)
 		var lxm = RandomGenerator.of("L128X128MixRandom");
 		var xoshiro = RandomGenerator.of("Xoshiro256PlusPlus");
+
+		// even works with custom implementations by using the class' simple name
+		var xkcd = RandomGenerator.of("Xkcd");
 	}
 
 	private static void moreInterfaces() {

src/main/java/org/codefx/demo/java17/api/random/Xkcd.java

@@ -5,11 +5,13 @@
 import java.util.random.RandomGenerator.ArbitrarilyJumpableGenerator;
 
 /*
- * It's possible to provide custom implementations of the generator interfaces that
- * get picked up by the generator factory API (including the `.of("name")` methods),
- * but that requires use of the JDK-internal annotation `@RandomGeneratorProperties`.
+ * It's possible to provide custom implementations of the generator interfaces by
+ * providing them as a service (see module declaration). Out of the box, that works
+ * with `RandomGenerator::of` (and on the other generator interfaces).
  *
- * While this works, the integration mechanism isn't meant for public use.
+ * By using the JDK-internal annotation `@RandomGeneratorProperties` (and possibly
+ * opening this package to java.base), it also works with `RandomGeneratorFactory`,
+ * but the integration mechanism isn't meant for public use.
  */
 
 @RandomGeneratorProperties(