signature: define SignatureEd25519

refs #4901

Change-Id: I71a962a6fd7df75b97d678e18db5b1e91078b7d7
diff --git a/changelog.rst b/changelog.rst
index ca0a61e..e65718a 100644
--- a/changelog.rst
+++ b/changelog.rst
@@ -46,6 +46,7 @@
 
   + Require all compliant implementations to support the ``SignatureSha256WithEcdsa`` signature type using NIST curve P-256
   + Redefine the signed portion of Data packets to be more future-proof
+  + Add ``SignatureEd25519`` signature type
 
 Version 0.2.1
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