release: Update version to 20260930

Write most relevant changes that happened since the last release. Move
the release notes to a markdown file for nice formatting compared to the
currently used txt file. Finally update the release number.

Signed-off-by: Maciej Wieczor-Retman <maciej.wieczor-retman@intel.com>
GitOrigin-RevId: e85aa3bebaae81ed1e6d163511ac7e1eafe732cf