docs: mention EntryDetail AddendaXX breaking change
## v0.4.0 (Unreleased)
+BREAKING CHANGES
+
+- `EntryDetail.Addendum` has been broken out into `Addenda02`, `Addenda05`, `Addenda98`, and `Addenda99` fields on `EntryDetail`.
+
ADDITIONS
- Support ACK, ATX, DNE, ENR StandardEntryClassCode (SEC types)
