feat(*): Add a contributor ladder

[calebschoepp]

Closes #1. This is a first draft of what our contributor ladder could look like. Let's discuss.

Inspiration

I took inspiration for this document from the following sources:

• https://gateway-api.sigs.k8s.io/contributing/contributor-ladder/
• https://github.com/kubernetes/community/blob/master/community-membership.md
• https://github.com/getporter/porter/blob/main/CONTRIBUTION_LADDER.md
• https://github.com/containerd/project/blob/main/GOVERNANCE.md

[calebschoepp]

Made a few more changes. We can talk about this and lock it in on our meeting this Friday.