docs: design doc for supporting aws sse:s3 in RGW
docs: design doc for supporting aws sse:s3 in RGW

The design doc for adding support in RGW for handling s3 requests with
sse:s3.

Signed-off-by: Jiffin Tony Thottan <c5f636a65220e122633e16282ed0de93ac96a4fd@redhat.com>

rook/rook,rook/rook,rook/rook,rook/rook,rook/rook