DOC: Added readme for RandomPassword

Provided instructions to create native executable

java/RandomPassword/PasswordGenerator.java

@@ -7,7 +7,7 @@ import java.util.ArrayList;
 import java.util.List;
 
 class PasswordGenerator {
-    private static final int DEFAULT_PASSWORD_LENGTH = 3;
+    private static final int DEFAULT_PASSWORD_LENGTH = 4;
 
     public static void main(String[] args) {
         try {

java/RandomPassword/README.md

@@ -0,0 +1,5 @@
+# Generate native image
+
+```bash
+native-image -Djava.io.tmpdir=~/tmp --parallelism=4 PasswordGenerator
+```