Add README file
Add README file

Signed-off-by: Esben Haabendal <esben.haabendal@prevas.dk>

(cherry picked from commit 64de15374d0f889fd8cc5bb7227203896280eba3)

oe-lite-rpi/base,oe-lite-rpi/base,jacobbarsoe/rpi-base,jacobbarsoe/rpi-base