coreos-download: add release note section
Adds a release note section on the overview page of Fedora CoreOS
Download. This gives users general information about the last
5 releases for each of stable, testing and next stream.
For each release, list the versions of important packages and package
information about what was added, removed, upgraded and downgraded. In
addition, for future improvements, adding notes on bugfix information
might also be helpful.
Signed-off-by: Allen Bai <abai@redhat.com>