doc: add new @option Doxygen ALIAS
doc: add new @option Doxygen ALIAS

This new ALIAS can be used to add references to Kconfig options. To use
it enclose the Kconfig symbol name like this `@option{KCONFIG_FOO}`.

Signed-off-by: Fabio Utzig <382671175562e0df8128054dbdb05a250d79f588@nordicsemi.no>

Vudentz/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,galak/zephyr,finikorg/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,Vudentz/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,Vudentz/zephyr,nashif/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr