Docs: add "Linux kernel extra" to manual install
Docs: add "Linux kernel extra" to manual install

Signed-off-by: Sebastiaan van Stijn <64b2b6d12bfe4baae7dad3d018f8cbf6b0e7a044@gone.nl>
(cherry picked from commit 8e2b20580b82c3d63d4dbbff1d6bee5640a46a8b)

solanolabs/docker,solanolabs/docker,solanolabs/docker