This commit adds a new GitHub Actions workflow for repository
lockdown. The workflow triggers when a pull request is opened, and it
notifies the contributor to use the OpenSBI mailing list for patch
reviews.
Additionally, the .gitignore file is updated to include the .github
directory.
Signed-off-by: Dongdong Zhang <zhangdongdong@eswincomputing.com>
Reviewed-by: Anup Patel <anup@branifault.org>