Include @maxbartel into IREE authors for citation (#24842)

As a follow-up on bff05a9d, include Maximilian Bartel as the sitting
chairman of the IREE TSC into the cited IREE authors list.

Signed-off-by: Artem Gindinson <gindinson@roofline.ai>

CITATION.cff

diff --git a/CITATION.cff b/CITATION.cff
index 3d4eadd..34f36f4 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -15,6 +15,10 @@
     given-names: Stella
     email: stellaraccident@gmail.com
     affiliation: Advanced Micro Devices, Inc.
+  - family-names: Bartel
+    given-names: Maximilian
+    email: bartel@roofline.ai
+    affiliation: RooflineAI GmbH
 license: "Apache-2.0 WITH LLVM-exception"
 url: "https://iree.dev/"
 repository-code: "https://github.com/iree-org/iree"