Document what needs to be done when adding a new curve
Document what needs to be done when adding a new curve

Signed-off-by: Gilles Peskine <f829db02715a0ea34b7c8e25097dae9e3517e831@arm.com>

ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,NXPmicro/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls,ARMmbed/mbedtls,NXPmicro/mbedtls,Mbed-TLS/mbedtls,ARMmbed/mbedtls