Update thinpool setup script in getting-started.md

[cauld]

Issue #, if available: N/A

Description of changes: The example thinpool setup in this guide script assumes the /var/lib/firecracker-containerd/snapshotter/devmapper directory exists. If fails if not. Added a directory check/create if needed block.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[Kern--]

Thanks, this looks good, but we need a DCO to merge.

You can use git commit -s if you've configured git to use your real name, otherwise you can manually add a line to your commit message like:

Signed-off-by: John Doe <[email protected]>

[cauld]

Added signed off

[Kern--]

The original commit and the merge are missing a sign off. Can you please rebase to remove the later commits and then modify the original commit to add the sign off?

[austinvazquez]

@cauld, can you squash locally and force push to your branch so that all commits are signed?