doc: add badge
doc: add badge

Signed-off-by: Anas Nashif <0d9952ec84ac43c159f6b7e7ed99a9080c00dd6e@intel.com>

zephyrproject-rtos/meta-zephyr-sdk,zephyrproject-rtos/meta-zephyr-sdk,zephyrproject-rtos/meta-zephyr-sdk,zephyrproject-rtos/meta-zephyr-sdk