Readme.rst: Add EmulatorPkg SECURE_BOOT_ENABLE CI status

Readme.rst: Add EmulatorPkg SECURE_BOOT_ENABLE CI status

https://bugzilla.tianocore.org/show_bug.cgi?id=2979

Add CI status badges for the EmulatorPkg CI builds with
SECURE_BOOT_ENABLE=TRUE for IA32/X64 and DEBUG/RELEASE/NOOPT.

Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Andrew Fish <afish@apple.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Divneil Rai Wadhawan <divneil.r.wadhawan@intel.com>
Cc: Sean Brogan <sean.brogan@microsoft.com>
Signed-off-by: Michael D Kinney <michael.d.kinney@intel.com>
Reviewed-by: Sean Brogan <sean.brogan@microsoft.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>