RedfishPkg: Add EDK2 Redfish Foundation diagrams

RedfishPkg: Add EDK2 Redfish Foundation diagrams

The Readme.md to delineate the EDK2 Redfish foundation driver
stack diagrams.

Signed-off-by: Abner Chang <abner.chang@hpe.com>
Cc: Jiaxin Wu <jiaxin.wu@intel.com>
Cc: Ting Ye <ting.ye@intel.com>
Cc: Siyuan Fu <siyuan.fu@intel.com>
Cc: Fan Wang <fan.wang@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Nickle Wang <nickle.wang@hpe.com>
Cc: Andrew Fish <afish@apple.com>
Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Nickle Wang <nickle.wang@hpe.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>