docs: Prepare release of version 2.1

Change-Id: I3694a8791b9540fc1b926a83ff55421b47e0f1b1
Refs: #3151
diff --git a/AUTHORS b/AUTHORS
index afa667d..3126cf4 100644
--- a/AUTHORS
+++ b/AUTHORS
@@ -15,3 +15,5 @@
   * Hovaidi Ardestani Mohammad  <mohammad.hovaidi.ardestani@aalto.fi>
   * Michael Sweatt              <https://www.linkedin.com/in/michaelsweatt>
   * Wentao Shang                <http://irl.cs.ucla.edu/~wentao/>
+  * Christian Kreuzberger       <christian.kreuzberger@itec.aau.at>
+  * Yuanzhi Gao                 <billmaxwell@ucla.edu>