Merge pull request k3s-io#357 from ibuildthecloud/docs

Add rootless docs

Merge pull request k3s-io#349 from erikwilson/missing-cgroup-pids-fix

Check for cgroup pids support

Merge pull request k3s-io#324 from erikwilson/configure-metrics

Configure aggregation layer for metrics

Merge pull request k3s-io#195 from ibuildthecloud/rootless

rootless

Merge pull request k3s-io#288 from erikwilson/airgap-initial-docs

Update README for airgap documentation