Add warning about deviating from the template format
Add warning about deviating from the template format

Detail the fact that the issue header is automatically parsed.

kjbracey-arm/mbed,mbedmicro/mbed,andcor02/mbed-os,mbedmicro/mbed,mbedmicro/mbed,mbedmicro/mbed,andcor02/mbed-os,kjbracey-arm/mbed,andcor02/mbed-os,kjbracey-arm/mbed,kjbracey-arm/mbed,andcor02/mbed-os,andcor02/mbed-os,mbedmicro/mbed,andcor02/mbed-os