Update CHANGES

CHANGES.md

@@ -1,5 +1,13 @@
 ## Unpublished
 
+- **[breaking]** PPX: Code to decode polyvariants doesn't use an additional
+  `_poly` function which was also generated by the PPX. Instead
+  `Unexpected_variant` error is used to signal that next decoder should be
+  tried.
+  ([#32](https://github.com/melange-community/melange-json/pull/32))
+- **[breaking]** Json.Decode.DecodeError exception now contains a variant type
+  as payload instead of a string.
+  ([#32](https://github.com/melange-community/melange-json/pull/32))
 - **[breaking]** PPX: Rename `[@json.as]` to `[@json.name]`
   ([#23](https://github.com/melange-community/melange-json/pull/23))
 - **[breaking]** PPX: Drop special encoding for enumeration-like variants (variants with each
@@ -10,6 +18,9 @@
   ([#27](https://github.com/melange-community/melange-json/pull/27))
 - **[breaking]** PPX: Consistent use of exceptions in runtime.
   ([#28](https://github.com/melange-community/melange-json/pull/28))
+- PPX: `[@@deriving json]` now can be used within signatures (this includes
+  `.mli` files).
+  ([#32](https://github.com/melange-community/melange-json/pull/32))
 - PPX: Add runtime for `result`
   ([#13](https://github.com/melange-community/melange-json/pull/13))
 - PPX: Add `yojson` as runtime dep for the native version