Document limitation of 1PC in JTS for JPA transactions

Please add new Important note in a section where information about working of "About Java Transaction Service (JTS)" will be written.
Node should contain the following information:
"JTS is limited to support single phase commit (1PC) in a one JVM.
The reason is, that after Transaction Manager enlists the resource locally, it calls sync, which doesn't have the transaction in its environment so tries to re-register. Re-registering makes transaction hierarchy being recreated, which causes a ServerTransaction to be created and registered with the (local) parent"