Bump up the envelop.md to version 1.1.0 and add change history.

Author: AdamZWu

envelope.md

@@ -2,7 +2,7 @@
 
 March 03, 2021
 
-Version 1.0.0
+Version 1.1.0
 
 This document describes the recommended data structure for storing DSSE
 signatures, which we call the "JSON Envelope". For the protocol/algorithm, see
@@ -89,3 +89,9 @@ invalidating the signature:
 
 At this point we do not standardize any other encoding. If a need arises, we may
 do so in the future.
+
+## Change history
+* 1.1.0:
+    * Added support for UTF-8 encoded payload and `payloadUtf8` field.
+
+* 1.0.0: Initial version