[release] Add missing CMakeLists.txt to tar ball.
(cherry picked from commit 59f99d0b97a192a3cac78caebd31e3ee3c722db4)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>
[release] Update list of copyright holders until Dune 2.3.
(cherry picked from commit 269e55e7239c95645880a28dee6bc94d9497efb9)

Signed-off-by: Christoph Grüninger <gruenich@dune-project.org>