Add .java to the list

The example webapp has sources. So why not ...
diff --git a/src/main/java/org/apache/tomcat/jakartaee/TextConverter.java b/src/main/java/org/apache/tomcat/jakartaee/TextConverter.java
index 9775964..bec3e7e 100644
--- a/src/main/java/org/apache/tomcat/jakartaee/TextConverter.java
+++ b/src/main/java/org/apache/tomcat/jakartaee/TextConverter.java
@@ -31,6 +31,7 @@
 
     static {
         supportedExtensions = new ArrayList<>();
+        supportedExtensions.add("java");
         supportedExtensions.add("jsp");
         supportedExtensions.add("jspx");
         supportedExtensions.add("tag");