Add a SECURITY.md file with hints for security researchers and other
parties who might report potential security vulnerabilities.
(From meta-yocto rev: e3c11a51dc814fdd400998f50b17e572d453e1d2)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Steve Sakoman <steve@sakoman.com>
