Update Moving from J to Namespace.md

Moving from J to Namespace.md

@@ -1,16 +1,29 @@
-Class map in J3:
+## Class map in J3:
 
 [https://github.com/joomla/joomla-cms/blob/3.10.12/libraries/classmap.php]
 
-Class map in J5:
+## Class map in J5:
 
 [https://github.com/joomla/joomla-cms/blob/5.0-dev/plugins/behaviour/compat/src/classmap/classmap.php]
 
-How to handle Classes that have no new counterparts like:
+## How to handle Classes that have no new counterparts like:
 
-- JError
+### JError
-  - JError::raiseError() should be replaced with native exceptions.
+- JError::raiseError() should be replaced with native exceptions.
-  - JError::raiseWarning() and JError::raiseNotice should be replaced with calls to application's enqueueMessage() method to display warnings/notices.
+- JError::raiseWarning() and JError::raiseNotice should be replaced with calls to application's enqueueMessage() method to display warnings/notices.
 
-More info on backwards compatible issues:
+This would mean you wrap your code in a try catch block and return the error. Someting like this:
+```
+try {
+    // Your code here;
+} catch (\RuntimeException $e) {
+    throw new \Exception($e->getMessage(), 500, $e);
+}
+```
+Or you would manually report an error back like this:
+```
+throw new \Exception(Text::_('Your error message here'), 500);
+```
+
+## More info on backwards compatible issues:
 [https://docs.joomla.org/Potential_backward_compatibility_issues_in_Joomla_4]