doc: add nodejs-sec email template

This commit adds a suggestion for a template to be used as part of the
security release process. One step of this process is to create an email
to nodejs-sec group and currently would contain a copy and pasted
version of what is published on nodejs.org. This suggestion is to
instead use a link to the blog post.

PR-URL: https://github.com/nodejs/node/pull/38290
Refs: https://github.com/nodejs/node/issues/38143


Reviewed-By: Michael Dawson <midawson@redhat.com>
Reviewed-By: James M Snell <jasnell@gmail.com>