cmake: boilerplate: Move app-library to be with its documentation
cmake: boilerplate: Move app-library to be with its documentation

Move documentation and declaration to be in the same place.

Signed-off-by: Mark Ruvald Pedersen <3c05dc905675c0722f67ee578faf639727313efa@oticon.com>

finikorg/zephyr,finikorg/zephyr,Vudentz/zephyr,explora26/zephyr,ldts/zephyr,explora26/zephyr,galak/zephyr,finikorg/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,ldts/zephyr,nashif/zephyr,galak/zephyr,explora26/zephyr,punitvara/zephyr,galak/zephyr,ldts/zephyr,GiulianoFranchetto/zephyr,GiulianoFranchetto/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,punitvara/zephyr,Vudentz/zephyr,zephyrproject-rtos/zephyr,nashif/zephyr,punitvara/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,explora26/zephyr,nashif/zephyr,GiulianoFranchetto/zephyr,Vudentz/zephyr,Vudentz/zephyr,ldts/zephyr,Vudentz/zephyr,galak/zephyr,finikorg/zephyr,Vudentz/zephyr