Add ChangeLog entry to credit independent contribution

Also: fixes #1437
diff --git a/ChangeLog b/ChangeLog
index aaf34fc..0293e49 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -54,6 +54,9 @@
      Wilson #481
    * Improve the documentation of mbedtls_net_accept(). Contributed by Ivan
      Krylov.
+   * Improve robustness of mbedtls_ssl_derive_keys against the use of
+     HMAC functions with non-HMAC ciphersuites. Independently contributed
+     by Jiayuan Chen in #1377. Fixes #1437.
 
 = mbed TLS 2.8.0 branch released 2018-03-16