Added fix for x448 bug to changelog.

Signed-off-by: Pol Henarejos <pol.henarejos@cttc.es>
diff --git a/ChangeLog.d/bug_x448.txt b/ChangeLog.d/bug_x448.txt
new file mode 100644
index 0000000..cebefc4
--- /dev/null
+++ b/ChangeLog.d/bug_x448.txt
@@ -0,0 +1,2 @@
+Bugfix
+    * Fix order value of curve x448.