doc: First process in container needs `Init: true`
doc: First process in container needs `Init: true`

`Init` on the `Process` struct specifies whether the process is the first process in the container. This needs to be set to `true` when running the container.

Signed-off-by: Andreas Stocker <907de10a5e6a9270c228a4a9c220ec2a9b9d868f@anexia-it.com>

justincormack/runc,justincormack/runc,dqminh/runc,dqminh/runc,rhatdan/runc,estesp/runc,mikebrow/runc,xiaochenshen/runc,mikebrow/runc,kolyshkin/runc,rhatdan/runc,opencontainers/runc,dqminh/runc,adrianreber/runc,mYmNeo/runc,kolyshkin/runc,xiaochenshen/runc,opencontainers/runc,mikebrow/runc,justincormack/runc,rhatdan/runc,opencontainers/runc,mYmNeo/runc,dqminh/runc,estesp/runc,adrianreber/runc,xiaochenshen/runc,mYmNeo/runc,adrianreber/runc,kolyshkin/runc,opencontainers/runc,rhatdan/runc,estesp/runc,kolyshkin/runc