"report a security issue" button was shown redundantly in https://github.com/containerd/containerd/issues/new/choose Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>
Add `.github/ISSUE_TEMPLATE/config.yml` to clarify where is the right place (in the most cases) to ask questions. Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>