Add a SECURITY.md file with hints for security researchers and other
parties who might report potential security vulnerabilities.
(From meta-yocto rev: d8b84cfded9137a74ab0052ff2d7710887f29f10)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
