Create self-service prep docs

[Avishai Ish-Shalom]

Create prep docs for people to read as a replacement for the prep talk. The docs should include:

• outline: list of subjects and required knowledge
• relevant links
• "further reading" list
• intro doc for relevant subjects

topics that needs to be covered in intro docs:

• what is a "linux container" made of
• glibc, userspace, kernelspace
• processes from the kernel PoV
• cgroups
• namespaces
• CoW storage (high level)
• chroot/pivot_root
• mounts
• users
• basic memory management (rlimit, oom killer, memory cgroup)

i suggest putting the docs as markdown in a "prep-docs" directory so people can consume directly from the repo